Aneurysmal Bone Cyst

Background

Aneurysmal bone cyst (ABC) is a benign tumor of bone. It most frequently develops in the metaphyses of long bones and the posterior elements of vertebral bodies. ABC may arise de novo (primary ABC), or areas resembling ABC can be found in other benign and malignant bone tumors that have undergone secondary cystic change (secondary ABC). These tumors may present with bone pain or swelling.

Recent studies have identified chromosomal abnormalities indicating that this tumor, once thought to be a reactive process, may actually be a neoplasm.

Outline

Epidemiology
Disease Associations
Pathogenesis
Laboratory/Radiologic/Other Diagnostic Testing
Gross Appearance and Clinical Variants
Histopathological Features and Variants
Special Stains/Immunohistochemistry/Electron Microscopy
Differential Diagnosis
Prognosis and Treatment
Commonly Used Terms

EPIDEMIOLOGY CHARACTERIZATION

SYNONYMS ABC

AGE RANGE-MEDIAN First 2 decades

SEX (M:F)
Equal

DISEASE ASSOCIATIONS CHARACTERIZATION

CYCLIC NEUTROPENIA

Solid variant of aneurysmal bone cyst in a patient with cyclic neutropenia.

Levendoglu-Tugal O, Slim M, Davidian MM, Klein S, Jayabose S.

Department of Pediatrics, New York Medical College, Valhalla 10595, USA.

Pediatr Hematol Oncol 1996 Nov-Dec;13(6):549-54 Abstract quote

A 16-year-old female with cyclic neutropenia (CN) was incidentally found to have a thoracic vertebral mass during the preoperative work-up for maxillary sinus surgery. An exploratory thoracotomy revealed a very vascular tumor involving T-10 and T-11 vertebral bodies.

Gross total resection of the tumor was achieved. Pathology revealed a solid variant of aneurysmal bone cyst. This is a rare benign neoplasm of bone more commonly seen in the mandible and facial bones as well as involving the small tubular bones of the hands and feet. Because of its rarity, location, and an unknown association with CN, we found this case worthwhile to publish.

PATHOGENESIS CHARACTERIZATION

GENERAL

Aneurysmal bone cyst: its pathogenesis based on angiographic, immunohistochemical and electron microscopic studies.

Szendroi M, Arato G, Ezzati A, Huttl K, Szavcsur P.

Department of Orthopaedics, Semmelweis University of Medicine, Budapest, Hungary.

Pathol Oncol Res 1998;4(4):277-81 Abstract quote

Based on angiographic, immunohistochemical as well as electron microscopic findings, authors outline a hypothesis for the etiopathogenesis of aneurysmal bone cysts.

No changes were found at the arterial site in 16 studied aneurysmal bone cysts, with no signs of an arteriovenous shunt. In certain cases, however, dilated and tortous efferent veins became visible in the late venous phase. Due to the impedance of venous flow, the intracystic pressure increases and the small veins become dilated causing formation of aneurysmal slits. This is supported by the immunohistochemical finding that S-actin shows concentric arrangement around the aneurysmal cavities. Endothelial lining and basal membrane remnants were detectable in places, though the aneurysmal slits were devoid of continuous endothelial lining and basal membrane.

We suggested that the aneurysmal bone cyst corresponds to a hemodynamic disturbance and is due to primary or secondary venous malformation of the bones.

CHROMOSOMAL ALTERATIONS

Recurrent t(16;17)(q22;p13) in aneurysmal bone cysts.

Panoutsakopoulos G, Pandis N, Kyriazoglou I, Gustafson P, Mertens F, Mandahl N.

Department of Genetics, Saint Savas Hospital, Athens, Greece.

Genes Chromosomes Cancer 1999 Nov;26(3):265-6 Abstract quote

Aneurysmal bone cyst (ABC) is a benign bone lesion for which no previous cytogenetic data exist.

We describe the finding of clonal chromosome aberrations in three tumors; two had a t(16;17)(q22;p13) as the sole anomaly, and the third had a del(16)(q22) as the only change.

These findings show that somatic mutations contribute to the development of ABC and furthermore indicate that bands 16q22 and 17p13 may harbor genes of importance in this process.

Aneurysmal bone cyst with chromosomal changes involving 7q and 16p.

Baruffi MR, Neto JB, Barbieri CH, Casartelli C.

Department of Genetics, School of Medicine of Ribeirao Preto, University of Sao Paulo, Av. Bandeirantes, 3900, 14049-900 Ribeirao Preto, Sao Paolo, Brazil.

Cancer Genet Cytogenet 2001 Sep;129(2):177-80 Abstract quote

An aneurysmal bone cyst was submitted to cytogenetic analysis. The modal chromosome number was 46. The composite karyotype was 40 approximately 48,XY,-Y[4],-6[3],del(7)(q32)[3],-9[3],+12[2],+13[2], inv(16)(p13.1q24)[4],-17[3],-19[4],-20[3][cp13]. The clonal structural changes detected were del(7)(q32) and inv(16)(p13.1q24). The breakpoints involved affected areas to which important genes for cell cycle regulation have been mapped.

There is only one report in the literature of three aneurysmal bone cysts presenting clonal karyotypic alterations. The cytogenetic study of the aneurysmal bone cyst reported here showed different results when compared to those previously described in the literature.

Aneurysmal bone cyst of the nose with 17p13 involvement.

Winnepenninckx V, Debiec-Rychter M, Jorissen M, Bogaerts S, Sciot R.

University Hospital St-Raphael, Department of Pathology, Katholieke Universiteit Leuven, Belgium.

Virchows Arch 2001 Nov;439(5):636-9 Abstract quote

We report on a 6-year-old girl with a polypoid mass, filling up the entire right nasal cavity as shown on a magnetic resonance imaging scan. Histologically, the tumor had the characteristics of an aneurysmal bone cyst, which is extremely rare in this location. Cytogenetic analysis disclosed a single (6:17)(p21;p13) translocation, confirming a specific genetic involvement in the development of aneurysmal bone cysts.

Fluorescent in situ hybridization analysis mapped the putative gene between the p53 (17p13.1) and the Mieller-Dieker gene (17p13.3) loci.

LABORATORY/RADIOLOGIC/
OTHER TESTS
CHARACTERIZATION

RADIOLOGIC Eccentric, lytic, and expansile with well-defined margins

X-RAYS

Radiological and clinical features of aneurysmal bone cyst of the jaws.

Kaffe I, Naor H, Calderon S, Buchner A.

Department of Oral Pathology and Oral Medicine, Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Israel.

Dentomaxillofac Radiol 1999 May;28(3):167-72 Abstract quote

PURPOSE: To evaluate the clinical and radiological features of aneurysmal bone cyst (ABC) of the jaws.

MATERIALS AND METHODS: A total of 64 cases (60 from the English-language literature and four new cases) were studied and critically evaluated with emphasis on the radiological features.

RESULTS: Age at time of initial diagnosis ranged from 4-78 years, with a mean age of 21.5 years and median age of 17 years. There were no differences in gender distribution. The ratio between the mandible and maxilla was 2.4:1. Ninety-two per cent of the lesions were located in the posterior region of the jaws. Lesions were radiolucent in 87% of cases, radiopaque in 2% and mixed in 11%. Fifty-three per cent were multilocular, 43% unilocular and 3% not loculated. The border of the lesions was defined but not corticated in 39%, well defined in 33% and diffuse in 28%.

CONCLUSIONS: ABC has a variable radiological appearance and should be considered in the differential diagnosis of any unilocular or multilocular radiolucent lesion of the jaws as well as any mixed radiolucent-radiopaque lesion.

MRI

Imaging of giant cell tumor and giant cell reparative granuloma of bone: radiologic-pathologic correlation.

Murphey MD, Nomikos GC, Flemming DJ, Gannon FH, Temple HT, Kransdorf MJ.

Department of Radiologic Pathology, Armed Forces Institute of Pathology, 6825 16th St NW, Bldg 54, Rm M-133A, Washington, DC 20306, USA.

Radiographics 2001 Sep-Oct;21(5):1283-309 Abstract quote

The radiologic features of giant cell tumor (GCT) and giant cell reparative granuloma (GCRG) of bone often strongly suggest the diagnosis and reflect their pathologic appearance.

At radiography, GCT often demonstrates a metaepiphyseal location with extension to subchondral bone. GCRG has a similar appearance but most commonly affects the mandible, maxilla, hands, or feet. Computed tomography and magnetic resonance (MR) imaging are helpful in staging lesions, particularly in delineating soft-tissue extension. Cystic (secondary aneurysmal bone cyst) components are reported in 14% of GCTs. However, biopsy must be directed at the solid regions, which harbor diagnostic tissue. These solid components demonstrate low to intermediate signal intensity at T2-weighted MR imaging, a feature that can be helpful in diagnosis. Multiple GCTs, although rare, do occur and may be associated with Paget disease. Malignant GCT accounts for 5%-10% of all GCTs and is usually secondary to previous irradiation of benign GCT.

Treatment of GCT usually consists of surgical resection. Recurrence is seen in 2%-25% of cases, and imaging is vital for early detection. Recognition of the spectrum of radiologic appearances of GCT and GCRG is important in allowing prospective diagnosis, guiding therapy, and facilitating early detection of recurrence.

LABORATORY MARKERS

GROSS APPEARANCE/
CLINICAL VARIANTS CHARACTERIZATION

GENERAL

VARIANTS

HUMERUS

Solid aneurysmal bone cyst in the humerus.

Yamamoto T, Marui T, Akisue T, Mizuno K.

Department of Orthopaedic Surgery, Kobe University School of Medicine, Japan.

Skeletal Radiol 2000 Aug;29(8):470-3 Abstract quote

We report on a 69-year-old woman with a solid variant of aneurysmal bone cyst (solid ABC) in the left humerus with a pathological fracture.

Radiographically, the lesion exhibited a relatively well-defined osteolytic lesion in the diaphysis of the left humerus. On magnetic resonance (MR) imaging, the medullary lesion exhibited a homogeneous signal intensity isointense with surrounding normal muscles on the T1-weighted images and a mixture of low and high signal intensity on the T2-weighted images. Contrast-enhanced T1-weighted images revealed diffuse enhancement of the entire lesion.

The pathological study showed a proliferation of fibroblasts, histiocytes, chronic inflammatory cells and numerous multinucleated giant cells in a collagenous matrix. Abundant osteoid formation in the matrix was observed, but the cells were devoid of nuclear atypia. Aneurysmal cystic cavities were absent. A review of the English literature found 22 cases of solid ABC of the long bones.

JAWS

Aneurysmal bone cysts of the jaws: clinicopathological features, radiographic evaluation and treatment analysis of 17 cases.

Kalantar Motamedi MH.

Clinic of Oral and Maxillofacial Surgery, Baqiyatallah Medical Center, Iran.

J Craniomaxillofac Surg 1998 Feb;26(1):56-62 Abstract quote

This article re-evaluates the various clinicopathological presentations and array of radiographic features displayed by aneurysmal bone cysts (ABCs) of the jaws.

In this retrospective clinical study, 17 cases of ABCs of the jaws surgically treated during an 11-year period from 1986-1997 are evaluated. The age and sex distribution, diagnostic characteristics, mode of treatment and long-term surgical results are presented and compared with the international literature. Investigation included serial clinical examinations, appropriate radiographic evaluation, CT scans and angiograms when indicated. All the patients had mandibular lesions and were managed by complete surgical curettage of the lesions. Ten were in males (58.8%) and seven (41.2%) in females. The mean age of occurrence was 21.05 years, ranging from 7 to 58 years.

Clinical presentation in these patients ranged from an asymptomatic incidental radiographic finding to an expanding, rapidly progressive and destructive lesion resulting in a pathological fracture. Radiographic findings varied from unicystic radiolucencies or moth-eaten radiolucencies to extensive multilocular lesions causing bilateral expansion and destruction of the mandibular cortices. Twelve of the patients (70.5%) could recall a history of trauma. Needle aspiration with a 16 or 18 guage needle was positive, producing syringes full of blood in all but two of the cases (88.2%). Six cases (35.2%) were extremely vascular and had increased rapidly in size, and three required angiographic studies for preoperative diagnosis and differentiation from other vascular entities. Nine of the cases (52.9%) were found in the mandibular angle-ramus area. Four cases (23.5%) required extraoral surgical access for curettage while the remainder were treated intraorally. During the follow-up period, which ranged from 2-11 years, no recurrences have occurred. Restoration of facial symmetry and bone formation has been favourable in all patients, despite the fact that grafts were not used.

This 11-year study shows that ABCs present with varied clinicopathological and radiographic features and thus may pose a diagnostic dilemma. As we have not noted any recurrences following surgical curettage of mandibular lesions, we feel that initial surgical resection or bone grafting is not necessary, provided that adequate access and complete curettage can be obtained.

SOFT TISSUE

Primary aneurysmal cyst of soft tissue. Report of a case with ultrastructural and MRI studies.

Lopez-Barea F, Rodriguez-Peralto JL, Burgos-Lizaldez E, Alvarez-Linera J, Sanchez-Herrera S.

Department of Anatomical Pathology, La Paz Hospital, Madrid, Spain.

Virchows Arch 1996 May;428(2):125-9 Abstract quote

We report a case of primary aneurysmal cyst of soft tissues in a 57-year-old woman presenting with a painful mass in her left arm. Conventional radiography showed a radiolucent soft tissue mass surrounded by a ring of bone. MRI displayed an unusual, ill-defined soft tissue lesion that was not connected to the nearby humerus and appeared to be an aggressive tumour.

Microscopically, the mass consisted of multiple anastomosing cavernous channels surrounded by a peripheral band of mature trabecular bone. These bloody channels were separated by fibrous septa containing fibroblasts, histiocytes and multinucleated giant cells, as well as fibromyxochondroid material. Some of these giant cells lined the septa and partially occupied the lumen of the channels. Ultrastructurally, the features observed in this tumour were similar to those described in aneurysmal bone cyst; the giant cells lining the septa were an additional observation.

Whereas most bone tumours have a well-known extraosseous counterpart, this unique lesion is not well recognized by surgical pathologists and the few published cases have been reported under different names. Gross, microscopic, radiological and ultrastructural findings are presented to familiarize pathologists with this underdiagnosed condition.

Aneurysmal cyst of soft tissue: report of a case with serial magnetic resonance imaging and biopsy.

Shannon P, Bedard Y, Bell R, Kandel R.

Department of Pathology and Laboratory Medicine, University of Toronto, Ontario, Canada.

Hum Pathol 1997 Feb;28(2):255-7 Abstract quote

We report a case of an extraosseous aneurysmal cyst arising in the left retroclavicular soft tissue of a 29-year-old woman.

A magnetic resonance imaging (MRI) scan showed a solid lesion within soft tissue, abutting the clavicle without bone involvement. An incisional biopsy was interpreted as showing osteoclast rich nodular fasciitis with prominent vascularity. A second MRI 5 months later showed intralesional cystic change with areas of increased signal on T2-weighted images, still without any bony defect. The lesion was excised.

Histological examination revealed large vascular spaces lined focally by giant cells. The remainder of the lesion was composed of an admixture of spindle cells and osteoclast-like giant cells. The histological and ultrastructural appearance was that of an aneurysmal bone cyst; however, in view of the lack of any bony involvement, a diagnosis of aneurysmal cyst of soft tissue was made.

Primary aneurysmal cysts of soft tissue are rare; this is the third well-documented case in the literature, and the first to describe both the MRI appearance and the histological evolution from a solid to multiloculated lesion.

Soft tissue aneurysmal bone cyst: a clinicopathologic study of five cases.

Nielsen GP, Fletcher CD, Smith MA, Rybak L, Rosenberg AE.

James Homer Wright Pathology Laboratories, Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.

Am J Surg Pathol 2002 Jan;26(1):64-9 Abstract quote

We describe five primary soft tissue tumors that had histologic features identical to intraosseous aneurysmal bone cyst. The tumors occurred in three females and two males, who ranged in age from 8 to 37 years (median 28 years). They arose in the deep soft tissue of the upper extremities, thigh, and groin region and typically presented as a rapidly growing mass; no involvement of the adjacent bones was identified. The tumors ranged in size from 2.5 to 9 cm (median 4 cm).

Grossly, they were surrounded by a thin rim of bone and on sectioning had hemorrhagic cystic spaces delineated by fibrous septa. Histologically, the cystic spaces were filled with blood and the fibrous septa were composed of fibroblasts, osteoclast-type giant cells, and woven bone. Cytogenetic analysis of one tumor showed 46,XY,t(17;17)(p13;q12), a result similar to that which has been reported for intraosseous aneurysmal bone cyst. The differential diagnosis includes a variety of bone-forming and giant cell-containing tumors, the most important being extraskeletal osteosarcoma.

Follow-up showed that four patients are free of disease 16 months to 10 years after surgery; one tumor regrew after incomplete initial excision, but the patient has been free of disease 16 months after a second operation.

Soft tissue aneurysmal bone cyst is an uncommon benign tumor that can be treated by simple excision, and it should be distinguished from a variety of other reactive and neoplastic processes.

SPINE

Aneurysmal bone cyst of the spine with familial incidence.

DiCaprio MR, Murphy MJ, Camp RL.

Departments of Orthopaedics and Rehabilitation and Pathology, Yale University School of Medicine, New Haven, CT 06520-8071, USA.

Spine 2000 Jun 15;25(12):1589-92 Abstract quote

STUDY DESIGN: A report of two cases of aneurysmal bone cysts of the spine occurring in a father and daughter.

OBJECTIVE: To present an unusual finding of familial incidence of aneurysmal bone cyst and review the literature.

SUMMARY OF BACKGROUND DATA: Aneurysmal bone cysts are benign, expanding, locally aggressive lesions. Up to 20% of cases involve the spine. The cause of primary aneurysmal bone cysts remains unclear. There have been three previous reports of a familial incidence supporting the importance of a hereditary component in the cause of aneurysmal bone cysts.

METHODS: A 36-year-old man and a 7-year-old girl were diagnosed with aneurysmal bone cyst involving the spine by clinical manifestations, radiographic features, and histologic evaluation.

RESULTS: The father remains recurrence- and symptom-free 6 years after primary resection. Five months after surgery, the daughter was found to have recurrent disease by magnetic resonance imaging and underwent a second procedure within 1 year of the primary resection.

CONCLUSION: The occurrence of a primary aneurysmal bone cyst in two family members, occurring at adjacent vertebral levels, is suggestive of a hereditary component to the formation of primary aneurysmal bone cyst.

Aneurysmal bone cyst of the mobile spine: report on 41 cases.

Boriani S, De Iure F, Campanacci L, Gasbarrini A, Bandiera S, Biagini R, Bertoni F, Picci P.

Department of Orthopedics and Traumatology, Maggiore Hospital, Bologna, Italy

Spine 2001 Jan 1;26(1):27-35 Abstract quote

STUDY DESIGN: Forty-one cases of aneurysmal bone cyst of the mobile spine were retrospectively reviewed.

OBJECTIVES: To evaluate the role of surgical and nonsurgical treatment of aneurysmal bone cyst of the spine.

SUMMARY OF BACKGROUND DATA: Ten to 30% of aneurysmal bone cysts arise from the mobile spine, frequently occurring in pediatric patients. The course of the disease depends on the aggressiveness of the tumor, as well as the treatment. Intralesional surgery seems to be an effective treatment, as well as radiotherapy and embolization.

METHODS: All charts, radiographs, and images were reviewed. The composite information provided by this review allowed for oncologic and surgical staging of these cases. Thirty-two patients underwent curettage (14 of them followed by radiotherapy), four were submitted to selective arterial embolization, three received radiotherapy alone, and two underwent en bloc-excision.

RESULTS: All patients were found alive and disease free at final follow-up evaluation. Two recurrences followed one incomplete curettage and one embolization. The combination of curettage and radiotherapy, although effective, showed the greatest incidence of late axial deformity. Selective arterial embolization was curative in three of four cases and did not affect the possibility of surgery in case of local recurrence.

CONCLUSIONS: If confirmed on larger series, selective arterial embolization seems to be the first treatment option for spine aneurysmal bone cyst, because of the low cost-to-benefit ratio. Diagnosis must be certain, based on pathognomonic radiographic pattern or on histologic study.- In case of neurologic involvement, pathologic fracture, technical impossibility of performing embolization, or local recurrence after at least two embolization procedures, complete intralesional excision would be the therapy of choice.

HISTOLOGICAL TYPES CHARACTERIZATION

GENERAL Blood-filled cystic spaces separated by fibrous septa that contain an admixture of fibroblasts, variable numbers of osteoclast-type giant cells, and reactive woven bone.

Aneurysmal bone cyst. A clinicopathologic study of 238 cases.

Vergel De Dios AM, Bond JR, Shives TC, McLeod RA, Unni KK.

Department of Diagnostic Radiology, Mayo Clinic, Rochester, Minnesota 55905.

Cancer 1992 Jun 15;69(12):2921-31 Abstract quote

Aneurysmal bone cyst (ABC) is a nonneoplastic expansile bone lesion that mainly affects children and young adults. Primary ABC is relatively rare, with an incidence one half that of giant cell tumor of bone.

In 238 patients with ABC studied in the Mayo Clinic files, more than 80% of the lesions were in long bones, flat bones, or the spinal column. Of the lesions initially treated at the Mayo Clinic, 95% were typical ABC; the rest were "solid" variants. Except for the absence of obvious cavernous channels and spaces, there was no significant histologic difference between solid variant and typical ABC. Radiographically, ABC is an eccentric expansile lesion commonly located at the metaphysis of long bones.

Computed tomography and magnetic resonance imaging may show multiple internal septations or fluid levels. In the 153 patients treated, 19% had recurrence after curettage (intralesional excision). Recurrence was most common during the first 2 postoperative years.

VARIANTS

SPECIAL STAINS/IMMUNOPEROXIDASE/
OTHER CHARACTERIZATION

SPECIAL STAINS

IMMUNOPEROXIDASE

FACTOR VIII

Endothelium in aneurysmal bone cyst.

Aho HJ, Aho AJ, Pelliniemi LJ, Ekfors TO, Foidart JM.

Histopathology 1985 Apr;9(4):381-7 Abstract quote

The surface of the large cystic spaces and dilated blood vessels in seven cases of aneurysmal bone cysts was studied.

The endothelium of the blood vessels was surrounded by a layer of collagen types IV and V, and the endothelial cells contained factor VIII related antigen demonstrated by the peroxidase anti-peroxidase technique. Some blood vessels were dilated resembling small aneurysmal spaces. The visible surfaces of the aneurysmal spaces were devoid of collagen types IV and V, and of factor VIII related antigen. Ultrastructural analysis of paraffin embedded sections did not show the characteristic fine structural features of endothelium covering the aneurysmal spaces.

It is concluded that the large spaces in aneurysmal bone cysts are devoid of basement membranes and endothelial cells. The absence of endothelium may explain the abundance of haemorrhages in these lesions. Immunocytochemical demonstration of endothelial antigen provides a valuable tool for the differential diagnosis between aneurysmal bone cysts and vascular tumours.

DIFFERENTIAL DIAGNOSIS KEY DIFFERENTIATING FEATURES

FRACTURE, PATHOLOGIC

Pathological fracture in non-ossifying fibroma with histological features simulating aneurysmal bone cyst.

Hoeffel C, Panuel M, Plenat F, Mainard L, Hoeffel JC.

Department of Radiology, Hopital Jeanne d'Arc, Toul, France.

Eur Radiol 1999;9(4):669-71 Abstract quote

A 12-year-old-girl presented with a fracture of an osteolytic lesion of the distal radius. A 7-year-old girl presented with a fracture of an osteolytic lesion of the femoral shaft.

In both cases it was a non-ossifying fibroma with fracture misdiagnosed at pathology as aneurysmal bone cyst. Fractures through non-ossifying fibromas may alter the histological pattern of the initial lesion in two ways: firstly, by the presence of blood pigments due to the fracture, and secondly, by formation of new bone.

Radiological-pathological correlation is essential to avoid histological errors after pathological fracture in a non-ossifying fibroma.

GIANT CELL REPARATIVE GRANULOMA

"Solid" variant of aneurysmal bone cyst (extragnathic giant cell reparative granuloma) in the axial skeleton and long bones. A study of its morphologic spectrum and distinction from allied giant cell lesions.

Oda Y, Tsuneyoshi M, Shinohara N.

Second Department of Pathology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.

Cancer 1992 Dec 1;70(11):2642-9 Abstract quote

BACKGROUND. Giant cell reparative granuloma is generally considered to be a benign tumor-like bone lesion. Its involvement of axial skeleton and long bones is rare.

METHODS. Seven cases of extragnathic giant cell reparative granuloma (GCRG), which arose in the axial skeleton and long bones, were analyzed clinicopathologically and compared with allied lesions consisting of 31 cases of aneurysmal bone cyst (ABC) and 83 cases of giant cell tumor of bone (GCT).

RESULTS. These occurred in patients ranging in age from 8-36 years; two were in the vertebrae; two, in the clavicles; one, in a rib; one, in the humerus; and one in the tibia. None of the patients with GCRG had a recurrence despite incomplete resection. Its skeletal distribution and average associated patient age were similar to those of ABC. Histologically, they were characterized by florid fibroblastic proliferation with osteoclast-like giant cell-rich areas, stromal hemorrhage, and newly formed bone or osteoid trabeculae. The histologic features could be found around either the characteristic aneurysmal cysts or sinuses, although they were lacking any large blood-filled spaces.

CONCLUSIONS. The overlapping clinical and histologic features between GCRG and ABC and their similar biologic behavior represent related responses to an intraosseous hemorrhage. The authors prefer to use the term "solid variant of aneurysmal bone cyst" to describe this lesion.

Giant cell reparative granuloma: a comparative clinicopathologic study of lesions in gnathic and extragnathic sites.

Yamaguchi T, Dorfman HD.

Section of Orthopaedic Pathology, Department of Orthopaedic Surgery, Montefiore Medical Center, Bronx, NY 10467-2490, USA.

Int J Surg Pathol 2001 Jul;9(3):189-200 Abstract quote

This study attempts to define the clinicopathologic aspects of extragnathic giant cell reparative granuloma (GCRG) by contrasting it with the much better recognized GCRG of jaw bones and highlights the manifestations that are unique to the extragnathic localization.

Ninety-one GCRGs of 89 patients, 22 in jaw bones and 69 in the extragnathic bones, were examined. Females were affected twice as frequently as males in both groups. The age distribution of extragnathic GCRGs overlaps that of gnathic counterparts. Small bones of the hands (17 lesions) and feet (16 lesions) were the most common sites for extragnathic lesions. The radiographic findings were nonspecific.

Histology of extragnathic lesions was closely similar to that of lesions affecting the jaw. These giant cell lesions should be distinguished from giant cell tumors.

OSTEOSARCOMA, SOFT TISSUE

Soft-tissue osteosarcoma with prominent aneurysmatic bone cyst-like features: a case report.

Laforga JB, Jover A, Martinez P.

Department of Pathology, Hospital Marina Alta, Denia, Spain.

Diagn Cytopathol 2001 Mar;24(3):209-14 Abstract quote

We describe the cytological features of a soft-tissue high-grade spindle and pleomorphic sarcoma. The smears showed hypercellularity composed of pleomorphic round and elongated cells, and a striking population of multinucleated osteoclast-type giant cells.

Microscopically the tumor showed multiple patterns such as highly cellular pleomorphic, less cellular, and hyalinized areas with neoplastic cartilage and osteoid, and areas with hemorrhage and multicystic appearance with numerous osteoclastic giant cells, resembling aneurysmal bone cysts.

Immunohistochemical studies showed positivity for vimentin, while chondroid tissue was positive for S-100, and osteoclastic giant cells stained positively for CD68.

Due to the varied microscopic patterns, the differential diagnosis included many tumors containing osteoclastic giant cells and osteochondroid tissue.

PROGNOSIS AND TREATMENT CHARACTERIZATION

PROGNOSTIC FACTORS

GENERAL

Aneurysmal bone cyst of the extremities. Factors related to local recurrence after curettage with a high-speed burr.

Gibbs CP Jr, Hefele MC, Peabody TD, Montag AG, Aithal V, Simon MA.

University of Chicago Hospitals and Clinics, Illinois 60637, USA.

J Bone Joint Surg Am 1999 Dec;81(12):1671-8 Abstract quote

BACKGROUND: Aneurysmal bone cyst is a benign, locally destructive lesion of bone. The rates of local recurrence after curettage have varied widely. Therefore, we performed a retrospective study of patients who had had an aneurysmal bone cyst in order to identify the rate of local recurrence and the prognostic factors related to local recurrence after use of contemporary methods of curettage with a high-speed burr.

METHODS: We reviewed the cases of forty patients who had been managed by the same surgeon for an aneurysmal bone cyst, as diagnosed on the basis of the latest pathological review, between January 1, 1976, and December 31, 1993. The patients were evaluated with regard to age, gender, the duration and type of symptoms, the presence or absence of pathological fracture, the status of the growth plate, the bone and part of the bone that were involved, the type of operative procedure, the outcome, the radiographic stage, the findings on magnetic resonance imaging and computerized tomography (when it became available) and on bone scintigraphy, and histological parameters. The median duration of follow-up was eighty-seven months (range, fifteen to 267 months). According to the criteria of Enneking, no patient had a stage-1 lesion (one with a surrounding rim of cortical bone), twenty-four had a stage-2 lesion (one with a clearly defined border but no cortical bone), and sixteen had a stage-3 lesion (one with no clearly defined border).

RESULTS: Of the forty patients, thirty-four had curettage with use of a high-speed burr. Of these thirty-four, twenty-two had filling of the defect with a cancellous autogenous graft; four, with a cancellous allograft; and three, with polymethylmethacrylate. In five patients, no material was put into the defect. The remaining six patients had resection through the margin of the lesion. Four (12 percent) of the thirty-four patients who had curettage had a local recurrence. No patient who had an excision through the margin of the lesion had a local recurrence. All local recurrences were in skeletally immature girls who were three, four, ten, and eleven years old. Univariate analysis with use of the chi-square, Fisher exact, and Wilcoxon log-rank tests showed that local recurrence was associated only with a young age (p = 0.0036) and open growth plates (p = 0.039). All local recurrences occurred within two years postoperatively, at two, seven, nine, and twenty-four months, and all were treated successfully with a second operation.

CONCLUSIONS: Rates of local control of almost 90 percent can be achieved with thorough curettage with use of a mechanical burr and without use of liquid nitrogen, phenol, or other adjuvants in patients who have an aneurysmal bone cyst of an extremity. A young age and open growth plates are associated with an increased risk of local recurrence.

MALIGNANT TRANSFORMATION

Malignant transformation of aneurysmal bone cyst, with an analysis of the literature.

Kyriakos M, Hardy D.

Lauren V. Ackerman Division of Surgical Pathology, Washington University School of Medicine, St. Louis, Missouri.

Cancer 1991 Oct 15;68(8):1770-80 Abstract quote

An 11-year-old girl had a lytic, benign-appearing, expansive lesion of the distal tibia radiologically interpreted as an aneurysmal bone cyst (ABC). Tissue from two extensive curettage procedures was also histologically diagnosed as ABC. Approximately 50 months after the onset of symptoms, and 28 months after her last curettage, a highly pleomorphic osteosarcoma developed. The patient had not received prior radiation therapy.

The cases in the literature of possible malignant transformation of ABC are reviewed. The authors separate their case from telangiectatic osteosarcoma, and from "aneurysmal bone cyst-like osteosarcoma."

PEDIATRIC

Aneurysmal bone cyst in children: analysis of twenty-seven patients.

Bollini G, Jouve JL, Cottalorda J, Petit P, Panuel M, Jacquemier M.

Hopital Enfants Timone, Marseille, France.

J Pediatr Orthop B 1998 Oct;7(4):274-85 Abstract quote

The authors have analyzed a retrospective series of 27 aneurysmal bone cysts (ABCs) in children and adolescents.

The average age at diagnosis was 10 years (range: 3 years 7 months to 16 years), with a mean follow-up of 5 years (range: 1 month to 13 years 9 months). Pathologic fractures (8 cases) and pain (8 cases) were the main reasons for consultation. Of five spinal ABC patients, four presented with neurologic involvement.

Although conventional radiology is useful for diagnosing ABCs, magnetic resonance imaging (MRI) is nevertheless the most important technique for checking the extent of the lesions. However, the diagnosis still must be based on the pathologic laboratory findings, even though this is sometimes difficult because of associated lesions. In lesions of the long bones, recurrence was observed after curettage in 5 of 12 cases. For this reason, simple resection or resection with reconstruction is recommended rather than curettage whenever possible.

When an ABC is in contact with the growth plate in young children, blunt curettage should be performed to preserve the child's growth potential. Subsequent recurrence usually is easier to treat than an epiphysiodesis bridge and its consequences. The surgical procedures used to preserve the growth plate are described, along with methods of bone construction after surgery.

TREATMENT

GENERAL

Treatment of aneurysmal bone cysts of the pelvis and sacrum.

Papagelopoulos PJ, Choudhury SN, Frassica FJ, Bond JR, Unni KK, Sim FH.

Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.

J Bone Joint Surg Am 2001 Nov;83-A(11):1674-81 Abstract quote

BACKGROUND: Aneurysmal bone cysts are benign, non-neoplastic, highly vascular bone lesions. The purpose of this study was to describe the prevalence, the clinical presentation, and the recurrence rate of aneurysmal bone cysts of the pelvis and sacrum and to examine the diagnostic and therapeutic options and prognosis for patients with this condition.

METHODS: Forty consecutive patients with an aneurysmal bone cyst of the pelvis and/or sacrum were treated from 1921 to 1996. Their medical records and radiographic and imaging studies were reviewed, and histological sections from the cysts were examined. Seventeen lesions were iliosacral, sixteen were acetabular, and seven were ischiopubic. Seven involved the hip joint, and two involved the sacroiliac joint. All twelve sacral lesions extended to more than one sacral segment and were associated with neurological signs and symptoms. Destructive acetabular lesions were associated with pathological fracture in five patients and with medial migration of the femoral head, hip subluxation, and hip dislocation in one patient each. The mean duration of follow-up was thirteen years (range, three to fifty-three years).

RESULTS: Thirty-five patients who were initially treated for a primary lesion had surgical treatment (twenty-one had excision-curettage and fourteen had intralesional excision); two patients also had adjuvant radiation therapy. Of the thirty-five patients, five (14%) had a local recurrence noted less than eighteen months after the operation. Of five patients initially treated for a recurrent lesion, one had a local recurrence. At the latest follow-up examination, all forty patients were disease-free and twenty-eight (70%) were asymptomatic. There were two deep infections.

CONCLUSION: Aneurysmal bone cysts of the pelvis and sacrum are usually aggressive lesions associated with substantial bone destruction, pathological fractures, and local recurrence. Current management recommendations include preoperative selective arterial embolization, excision-curettage, and bone-grafting.

ENDOSCOPIC CURETTAGE

A new treatment of aneurysmal bone cyst by endoscopic curettage without bone grafting.

Otsuka T, Kobayashi M, Sekiya I, Yonezawa M, Kamiyama F, Matsushita Y, Matsui N.

Department of Orthopaedic Surgery, Nagoya City University Medical School, Nagoya City, Japan.

Arthroscopy 2001 Sep;17(7):E28 Abstract quote

Curettage and bone grafting are the accepted methods of treatment of aneurysmal bone cysts. Unfortunately, recurrence is common.

We treated 4 patients with atypical aneurysmal bone cysts that lacked aneurysmal dilatation by endoscopic curettage without bone grafting. New bone formation and remodeling were observed in all patients.

In the patients in whom the follow-up was longer than 30 months, there was no evidence of recurrence. Endoscopic curettage without bone grafting is a simple and effective treatment for aneurysmal bone cysts.

RADIATION

Megavoltage radiotherapy for aneurysmal bone cysts.

Feigenberg SJ, Marcus RB Jr, Zlotecki RA, Scarborough MT, Berrey BH, Enneking WF.

Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL 32610, USA.

Int J Radiat Oncol Biol Phys 2001 Apr 1;49(5):1243-7 Abstract quote

PURPOSE: An aneurysmal bone cyst (ABC) is a rapidly expansile and destructive benign tumor of bone that is usually treated by curettage and bone graft, with or without adjuvant treatment. For recurrent tumors, or tumors for which surgery would result in significant functional morbidity, does radiotherapy (RT) provide a safe and effective alternative for local control?

PATIENTS AND METHODS: Nine patients with histologically diagnosed aneurysmal bone cysts without other associated benign or malignant tumors were treated at the University of Florida with megavoltage RT between February 1964 and June 1992. The patients received local radiotherapy doses between 20 and 60 Gy, with 6 patients receiving 26--30 Gy. In 6 patients the diagnosis was made by biopsy alone; 3 underwent intralesional curettage before RT. Minimum follow-up was 20 months; 7 of 9 patients (77%) had follow-up greater than 11 years.

RESULTS: No patient experienced a local recurrence (median follow-up, 17 years). One patient required stabilization of the cervical spine 10 months after RT because of dorsal kyphosis from vertebral body collapse. No other significant side effects were experienced, and no patients developed secondary malignancies. Four patients were lost to follow-up: at 20 months, 11.5 years, 17 years, and 20 years after the initiation of treatment, none with any evidence of local recurrence. All of the patients who had significant pain before RT had relief of their symptoms within 2 weeks of completion of therapy.

CONCLUSIONS: Using modern-day RT, patients with recurrent or inoperable aneurysmal bone cysts can be treated effectively (with minimal toxicity) using a prescribed tumor dose of 26--30 Gy.

Rosai J. Ackerman's Surgical Pathology. Eight Edition. Mosby 1996.
Sternberg S. Diagnostic Surgical Pathology. Third Edition. Lipincott Williams and Wilkins 1999.

Commonly Used Terms

Bone Tumors

Soft Tissue Tumors

Last Updated 1/18/2002

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GROSS APPEARANCE/ CLINICAL VARIANTS	CHARACTERIZATION
GENERAL
VARIANTS
HUMERUS
Solid aneurysmal bone cyst in the humerus. Yamamoto T, Marui T, Akisue T, Mizuno K. Department of Orthopaedic Surgery, Kobe University School of Medicine, Japan.	Skeletal Radiol 2000 Aug;29(8):470-3 Abstract quote We report on a 69-year-old woman with a solid variant of aneurysmal bone cyst (solid ABC) in the left humerus with a pathological fracture. Radiographically, the lesion exhibited a relatively well-defined osteolytic lesion in the diaphysis of the left humerus. On magnetic resonance (MR) imaging, the medullary lesion exhibited a homogeneous signal intensity isointense with surrounding normal muscles on the T1-weighted images and a mixture of low and high signal intensity on the T2-weighted images. Contrast-enhanced T1-weighted images revealed diffuse enhancement of the entire lesion. The pathological study showed a proliferation of fibroblasts, histiocytes, chronic inflammatory cells and numerous multinucleated giant cells in a collagenous matrix. Abundant osteoid formation in the matrix was observed, but the cells were devoid of nuclear atypia. Aneurysmal cystic cavities were absent. A review of the English literature found 22 cases of solid ABC of the long bones.
JAWS
Aneurysmal bone cysts of the jaws: clinicopathological features, radiographic evaluation and treatment analysis of 17 cases. Kalantar Motamedi MH. Clinic of Oral and Maxillofacial Surgery, Baqiyatallah Medical Center, Iran.	J Craniomaxillofac Surg 1998 Feb;26(1):56-62 Abstract quote This article re-evaluates the various clinicopathological presentations and array of radiographic features displayed by aneurysmal bone cysts (ABCs) of the jaws. In this retrospective clinical study, 17 cases of ABCs of the jaws surgically treated during an 11-year period from 1986-1997 are evaluated. The age and sex distribution, diagnostic characteristics, mode of treatment and long-term surgical results are presented and compared with the international literature. Investigation included serial clinical examinations, appropriate radiographic evaluation, CT scans and angiograms when indicated. All the patients had mandibular lesions and were managed by complete surgical curettage of the lesions. Ten were in males (58.8%) and seven (41.2%) in females. The mean age of occurrence was 21.05 years, ranging from 7 to 58 years. Clinical presentation in these patients ranged from an asymptomatic incidental radiographic finding to an expanding, rapidly progressive and destructive lesion resulting in a pathological fracture. Radiographic findings varied from unicystic radiolucencies or moth-eaten radiolucencies to extensive multilocular lesions causing bilateral expansion and destruction of the mandibular cortices. Twelve of the patients (70.5%) could recall a history of trauma. Needle aspiration with a 16 or 18 guage needle was positive, producing syringes full of blood in all but two of the cases (88.2%). Six cases (35.2%) were extremely vascular and had increased rapidly in size, and three required angiographic studies for preoperative diagnosis and differentiation from other vascular entities. Nine of the cases (52.9%) were found in the mandibular angle-ramus area. Four cases (23.5%) required extraoral surgical access for curettage while the remainder were treated intraorally. During the follow-up period, which ranged from 2-11 years, no recurrences have occurred. Restoration of facial symmetry and bone formation has been favourable in all patients, despite the fact that grafts were not used. This 11-year study shows that ABCs present with varied clinicopathological and radiographic features and thus may pose a diagnostic dilemma. As we have not noted any recurrences following surgical curettage of mandibular lesions, we feel that initial surgical resection or bone grafting is not necessary, provided that adequate access and complete curettage can be obtained.
SOFT TISSUE
Primary aneurysmal cyst of soft tissue. Report of a case with ultrastructural and MRI studies. Lopez-Barea F, Rodriguez-Peralto JL, Burgos-Lizaldez E, Alvarez-Linera J, Sanchez-Herrera S. Department of Anatomical Pathology, La Paz Hospital, Madrid, Spain.	Virchows Arch 1996 May;428(2):125-9 Abstract quote We report a case of primary aneurysmal cyst of soft tissues in a 57-year-old woman presenting with a painful mass in her left arm. Conventional radiography showed a radiolucent soft tissue mass surrounded by a ring of bone. MRI displayed an unusual, ill-defined soft tissue lesion that was not connected to the nearby humerus and appeared to be an aggressive tumour. Microscopically, the mass consisted of multiple anastomosing cavernous channels surrounded by a peripheral band of mature trabecular bone. These bloody channels were separated by fibrous septa containing fibroblasts, histiocytes and multinucleated giant cells, as well as fibromyxochondroid material. Some of these giant cells lined the septa and partially occupied the lumen of the channels. Ultrastructurally, the features observed in this tumour were similar to those described in aneurysmal bone cyst; the giant cells lining the septa were an additional observation. Whereas most bone tumours have a well-known extraosseous counterpart, this unique lesion is not well recognized by surgical pathologists and the few published cases have been reported under different names. Gross, microscopic, radiological and ultrastructural findings are presented to familiarize pathologists with this underdiagnosed condition.
Aneurysmal cyst of soft tissue: report of a case with serial magnetic resonance imaging and biopsy. Shannon P, Bedard Y, Bell R, Kandel R. Department of Pathology and Laboratory Medicine, University of Toronto, Ontario, Canada.	Hum Pathol 1997 Feb;28(2):255-7 Abstract quote We report a case of an extraosseous aneurysmal cyst arising in the left retroclavicular soft tissue of a 29-year-old woman. A magnetic resonance imaging (MRI) scan showed a solid lesion within soft tissue, abutting the clavicle without bone involvement. An incisional biopsy was interpreted as showing osteoclast rich nodular fasciitis with prominent vascularity. A second MRI 5 months later showed intralesional cystic change with areas of increased signal on T2-weighted images, still without any bony defect. The lesion was excised. Histological examination revealed large vascular spaces lined focally by giant cells. The remainder of the lesion was composed of an admixture of spindle cells and osteoclast-like giant cells. The histological and ultrastructural appearance was that of an aneurysmal bone cyst; however, in view of the lack of any bony involvement, a diagnosis of aneurysmal cyst of soft tissue was made. Primary aneurysmal cysts of soft tissue are rare; this is the third well-documented case in the literature, and the first to describe both the MRI appearance and the histological evolution from a solid to multiloculated lesion.
Soft tissue aneurysmal bone cyst: a clinicopathologic study of five cases. Nielsen GP, Fletcher CD, Smith MA, Rybak L, Rosenberg AE. James Homer Wright Pathology Laboratories, Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.	Am J Surg Pathol 2002 Jan;26(1):64-9 Abstract quote We describe five primary soft tissue tumors that had histologic features identical to intraosseous aneurysmal bone cyst. The tumors occurred in three females and two males, who ranged in age from 8 to 37 years (median 28 years). They arose in the deep soft tissue of the upper extremities, thigh, and groin region and typically presented as a rapidly growing mass; no involvement of the adjacent bones was identified. The tumors ranged in size from 2.5 to 9 cm (median 4 cm). Grossly, they were surrounded by a thin rim of bone and on sectioning had hemorrhagic cystic spaces delineated by fibrous septa. Histologically, the cystic spaces were filled with blood and the fibrous septa were composed of fibroblasts, osteoclast-type giant cells, and woven bone. Cytogenetic analysis of one tumor showed 46,XY,t(17;17)(p13;q12), a result similar to that which has been reported for intraosseous aneurysmal bone cyst. The differential diagnosis includes a variety of bone-forming and giant cell-containing tumors, the most important being extraskeletal osteosarcoma. Follow-up showed that four patients are free of disease 16 months to 10 years after surgery; one tumor regrew after incomplete initial excision, but the patient has been free of disease 16 months after a second operation. Soft tissue aneurysmal bone cyst is an uncommon benign tumor that can be treated by simple excision, and it should be distinguished from a variety of other reactive and neoplastic processes.
SPINE
Aneurysmal bone cyst of the spine with familial incidence. DiCaprio MR, Murphy MJ, Camp RL. Departments of Orthopaedics and Rehabilitation and Pathology, Yale University School of Medicine, New Haven, CT 06520-8071, USA.	Spine 2000 Jun 15;25(12):1589-92 Abstract quote STUDY DESIGN: A report of two cases of aneurysmal bone cysts of the spine occurring in a father and daughter. OBJECTIVE: To present an unusual finding of familial incidence of aneurysmal bone cyst and review the literature. SUMMARY OF BACKGROUND DATA: Aneurysmal bone cysts are benign, expanding, locally aggressive lesions. Up to 20% of cases involve the spine. The cause of primary aneurysmal bone cysts remains unclear. There have been three previous reports of a familial incidence supporting the importance of a hereditary component in the cause of aneurysmal bone cysts. METHODS: A 36-year-old man and a 7-year-old girl were diagnosed with aneurysmal bone cyst involving the spine by clinical manifestations, radiographic features, and histologic evaluation. RESULTS: The father remains recurrence- and symptom-free 6 years after primary resection. Five months after surgery, the daughter was found to have recurrent disease by magnetic resonance imaging and underwent a second procedure within 1 year of the primary resection. CONCLUSION: The occurrence of a primary aneurysmal bone cyst in two family members, occurring at adjacent vertebral levels, is suggestive of a hereditary component to the formation of primary aneurysmal bone cyst.
Aneurysmal bone cyst of the mobile spine: report on 41 cases. Boriani S, De Iure F, Campanacci L, Gasbarrini A, Bandiera S, Biagini R, Bertoni F, Picci P. Department of Orthopedics and Traumatology, Maggiore Hospital, Bologna, Italy	Spine 2001 Jan 1;26(1):27-35 Abstract quote STUDY DESIGN: Forty-one cases of aneurysmal bone cyst of the mobile spine were retrospectively reviewed. OBJECTIVES: To evaluate the role of surgical and nonsurgical treatment of aneurysmal bone cyst of the spine. SUMMARY OF BACKGROUND DATA: Ten to 30% of aneurysmal bone cysts arise from the mobile spine, frequently occurring in pediatric patients. The course of the disease depends on the aggressiveness of the tumor, as well as the treatment. Intralesional surgery seems to be an effective treatment, as well as radiotherapy and embolization. METHODS: All charts, radiographs, and images were reviewed. The composite information provided by this review allowed for oncologic and surgical staging of these cases. Thirty-two patients underwent curettage (14 of them followed by radiotherapy), four were submitted to selective arterial embolization, three received radiotherapy alone, and two underwent en bloc-excision. RESULTS: All patients were found alive and disease free at final follow-up evaluation. Two recurrences followed one incomplete curettage and one embolization. The combination of curettage and radiotherapy, although effective, showed the greatest incidence of late axial deformity. Selective arterial embolization was curative in three of four cases and did not affect the possibility of surgery in case of local recurrence. CONCLUSIONS: If confirmed on larger series, selective arterial embolization seems to be the first treatment option for spine aneurysmal bone cyst, because of the low cost-to-benefit ratio. Diagnosis must be certain, based on pathognomonic radiographic pattern or on histologic study.- In case of neurologic involvement, pathologic fracture, technical impossibility of performing embolization, or local recurrence after at least two embolization procedures, complete intralesional excision would be the therapy of choice.

DIFFERENTIAL DIAGNOSIS	KEY DIFFERENTIATING FEATURES
FRACTURE, PATHOLOGIC
Pathological fracture in non-ossifying fibroma with histological features simulating aneurysmal bone cyst. Hoeffel C, Panuel M, Plenat F, Mainard L, Hoeffel JC. Department of Radiology, Hopital Jeanne d'Arc, Toul, France.	Eur Radiol 1999;9(4):669-71 Abstract quote A 12-year-old-girl presented with a fracture of an osteolytic lesion of the distal radius. A 7-year-old girl presented with a fracture of an osteolytic lesion of the femoral shaft. In both cases it was a non-ossifying fibroma with fracture misdiagnosed at pathology as aneurysmal bone cyst. Fractures through non-ossifying fibromas may alter the histological pattern of the initial lesion in two ways: firstly, by the presence of blood pigments due to the fracture, and secondly, by formation of new bone. Radiological-pathological correlation is essential to avoid histological errors after pathological fracture in a non-ossifying fibroma.
GIANT CELL REPARATIVE GRANULOMA
"Solid" variant of aneurysmal bone cyst (extragnathic giant cell reparative granuloma) in the axial skeleton and long bones. A study of its morphologic spectrum and distinction from allied giant cell lesions. Oda Y, Tsuneyoshi M, Shinohara N. Second Department of Pathology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.	Cancer 1992 Dec 1;70(11):2642-9 Abstract quote BACKGROUND. Giant cell reparative granuloma is generally considered to be a benign tumor-like bone lesion. Its involvement of axial skeleton and long bones is rare. METHODS. Seven cases of extragnathic giant cell reparative granuloma (GCRG), which arose in the axial skeleton and long bones, were analyzed clinicopathologically and compared with allied lesions consisting of 31 cases of aneurysmal bone cyst (ABC) and 83 cases of giant cell tumor of bone (GCT). RESULTS. These occurred in patients ranging in age from 8-36 years; two were in the vertebrae; two, in the clavicles; one, in a rib; one, in the humerus; and one in the tibia. None of the patients with GCRG had a recurrence despite incomplete resection. Its skeletal distribution and average associated patient age were similar to those of ABC. Histologically, they were characterized by florid fibroblastic proliferation with osteoclast-like giant cell-rich areas, stromal hemorrhage, and newly formed bone or osteoid trabeculae. The histologic features could be found around either the characteristic aneurysmal cysts or sinuses, although they were lacking any large blood-filled spaces. CONCLUSIONS. The overlapping clinical and histologic features between GCRG and ABC and their similar biologic behavior represent related responses to an intraosseous hemorrhage. The authors prefer to use the term "solid variant of aneurysmal bone cyst" to describe this lesion.
Giant cell reparative granuloma: a comparative clinicopathologic study of lesions in gnathic and extragnathic sites. Yamaguchi T, Dorfman HD. Section of Orthopaedic Pathology, Department of Orthopaedic Surgery, Montefiore Medical Center, Bronx, NY 10467-2490, USA.	Int J Surg Pathol 2001 Jul;9(3):189-200 Abstract quote This study attempts to define the clinicopathologic aspects of extragnathic giant cell reparative granuloma (GCRG) by contrasting it with the much better recognized GCRG of jaw bones and highlights the manifestations that are unique to the extragnathic localization. Ninety-one GCRGs of 89 patients, 22 in jaw bones and 69 in the extragnathic bones, were examined. Females were affected twice as frequently as males in both groups. The age distribution of extragnathic GCRGs overlaps that of gnathic counterparts. Small bones of the hands (17 lesions) and feet (16 lesions) were the most common sites for extragnathic lesions. The radiographic findings were nonspecific. Histology of extragnathic lesions was closely similar to that of lesions affecting the jaw. These giant cell lesions should be distinguished from giant cell tumors.
OSTEOSARCOMA, SOFT TISSUE
Soft-tissue osteosarcoma with prominent aneurysmatic bone cyst-like features: a case report. Laforga JB, Jover A, Martinez P. Department of Pathology, Hospital Marina Alta, Denia, Spain.	Diagn Cytopathol 2001 Mar;24(3):209-14 Abstract quote We describe the cytological features of a soft-tissue high-grade spindle and pleomorphic sarcoma. The smears showed hypercellularity composed of pleomorphic round and elongated cells, and a striking population of multinucleated osteoclast-type giant cells. Microscopically the tumor showed multiple patterns such as highly cellular pleomorphic, less cellular, and hyalinized areas with neoplastic cartilage and osteoid, and areas with hemorrhage and multicystic appearance with numerous osteoclastic giant cells, resembling aneurysmal bone cysts. Immunohistochemical studies showed positivity for vimentin, while chondroid tissue was positive for S-100, and osteoclastic giant cells stained positively for CD68. Due to the varied microscopic patterns, the differential diagnosis included many tumors containing osteoclastic giant cells and osteochondroid tissue.

PROGNOSIS AND TREATMENT	CHARACTERIZATION
PROGNOSTIC FACTORS
GENERAL
Aneurysmal bone cyst of the extremities. Factors related to local recurrence after curettage with a high-speed burr. Gibbs CP Jr, Hefele MC, Peabody TD, Montag AG, Aithal V, Simon MA. University of Chicago Hospitals and Clinics, Illinois 60637, USA.	J Bone Joint Surg Am 1999 Dec;81(12):1671-8 Abstract quote BACKGROUND: Aneurysmal bone cyst is a benign, locally destructive lesion of bone. The rates of local recurrence after curettage have varied widely. Therefore, we performed a retrospective study of patients who had had an aneurysmal bone cyst in order to identify the rate of local recurrence and the prognostic factors related to local recurrence after use of contemporary methods of curettage with a high-speed burr. METHODS: We reviewed the cases of forty patients who had been managed by the same surgeon for an aneurysmal bone cyst, as diagnosed on the basis of the latest pathological review, between January 1, 1976, and December 31, 1993. The patients were evaluated with regard to age, gender, the duration and type of symptoms, the presence or absence of pathological fracture, the status of the growth plate, the bone and part of the bone that were involved, the type of operative procedure, the outcome, the radiographic stage, the findings on magnetic resonance imaging and computerized tomography (when it became available) and on bone scintigraphy, and histological parameters. The median duration of follow-up was eighty-seven months (range, fifteen to 267 months). According to the criteria of Enneking, no patient had a stage-1 lesion (one with a surrounding rim of cortical bone), twenty-four had a stage-2 lesion (one with a clearly defined border but no cortical bone), and sixteen had a stage-3 lesion (one with no clearly defined border). RESULTS: Of the forty patients, thirty-four had curettage with use of a high-speed burr. Of these thirty-four, twenty-two had filling of the defect with a cancellous autogenous graft; four, with a cancellous allograft; and three, with polymethylmethacrylate. In five patients, no material was put into the defect. The remaining six patients had resection through the margin of the lesion. Four (12 percent) of the thirty-four patients who had curettage had a local recurrence. No patient who had an excision through the margin of the lesion had a local recurrence. All local recurrences were in skeletally immature girls who were three, four, ten, and eleven years old. Univariate analysis with use of the chi-square, Fisher exact, and Wilcoxon log-rank tests showed that local recurrence was associated only with a young age (p = 0.0036) and open growth plates (p = 0.039). All local recurrences occurred within two years postoperatively, at two, seven, nine, and twenty-four months, and all were treated successfully with a second operation. CONCLUSIONS: Rates of local control of almost 90 percent can be achieved with thorough curettage with use of a mechanical burr and without use of liquid nitrogen, phenol, or other adjuvants in patients who have an aneurysmal bone cyst of an extremity. A young age and open growth plates are associated with an increased risk of local recurrence.
MALIGNANT TRANSFORMATION
Malignant transformation of aneurysmal bone cyst, with an analysis of the literature. Kyriakos M, Hardy D. Lauren V. Ackerman Division of Surgical Pathology, Washington University School of Medicine, St. Louis, Missouri.	Cancer 1991 Oct 15;68(8):1770-80 Abstract quote An 11-year-old girl had a lytic, benign-appearing, expansive lesion of the distal tibia radiologically interpreted as an aneurysmal bone cyst (ABC). Tissue from two extensive curettage procedures was also histologically diagnosed as ABC. Approximately 50 months after the onset of symptoms, and 28 months after her last curettage, a highly pleomorphic osteosarcoma developed. The patient had not received prior radiation therapy. The cases in the literature of possible malignant transformation of ABC are reviewed. The authors separate their case from telangiectatic osteosarcoma, and from "aneurysmal bone cyst-like osteosarcoma."
PEDIATRIC
Aneurysmal bone cyst in children: analysis of twenty-seven patients. Bollini G, Jouve JL, Cottalorda J, Petit P, Panuel M, Jacquemier M. Hopital Enfants Timone, Marseille, France.	J Pediatr Orthop B 1998 Oct;7(4):274-85 Abstract quote The authors have analyzed a retrospective series of 27 aneurysmal bone cysts (ABCs) in children and adolescents. The average age at diagnosis was 10 years (range: 3 years 7 months to 16 years), with a mean follow-up of 5 years (range: 1 month to 13 years 9 months). Pathologic fractures (8 cases) and pain (8 cases) were the main reasons for consultation. Of five spinal ABC patients, four presented with neurologic involvement. Although conventional radiology is useful for diagnosing ABCs, magnetic resonance imaging (MRI) is nevertheless the most important technique for checking the extent of the lesions. However, the diagnosis still must be based on the pathologic laboratory findings, even though this is sometimes difficult because of associated lesions. In lesions of the long bones, recurrence was observed after curettage in 5 of 12 cases. For this reason, simple resection or resection with reconstruction is recommended rather than curettage whenever possible. When an ABC is in contact with the growth plate in young children, blunt curettage should be performed to preserve the child's growth potential. Subsequent recurrence usually is easier to treat than an epiphysiodesis bridge and its consequences. The surgical procedures used to preserve the growth plate are described, along with methods of bone construction after surgery.
TREATMENT
GENERAL
Treatment of aneurysmal bone cysts of the pelvis and sacrum. Papagelopoulos PJ, Choudhury SN, Frassica FJ, Bond JR, Unni KK, Sim FH. Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.	J Bone Joint Surg Am 2001 Nov;83-A(11):1674-81 Abstract quote BACKGROUND: Aneurysmal bone cysts are benign, non-neoplastic, highly vascular bone lesions. The purpose of this study was to describe the prevalence, the clinical presentation, and the recurrence rate of aneurysmal bone cysts of the pelvis and sacrum and to examine the diagnostic and therapeutic options and prognosis for patients with this condition. METHODS: Forty consecutive patients with an aneurysmal bone cyst of the pelvis and/or sacrum were treated from 1921 to 1996. Their medical records and radiographic and imaging studies were reviewed, and histological sections from the cysts were examined. Seventeen lesions were iliosacral, sixteen were acetabular, and seven were ischiopubic. Seven involved the hip joint, and two involved the sacroiliac joint. All twelve sacral lesions extended to more than one sacral segment and were associated with neurological signs and symptoms. Destructive acetabular lesions were associated with pathological fracture in five patients and with medial migration of the femoral head, hip subluxation, and hip dislocation in one patient each. The mean duration of follow-up was thirteen years (range, three to fifty-three years). RESULTS: Thirty-five patients who were initially treated for a primary lesion had surgical treatment (twenty-one had excision-curettage and fourteen had intralesional excision); two patients also had adjuvant radiation therapy. Of the thirty-five patients, five (14%) had a local recurrence noted less than eighteen months after the operation. Of five patients initially treated for a recurrent lesion, one had a local recurrence. At the latest follow-up examination, all forty patients were disease-free and twenty-eight (70%) were asymptomatic. There were two deep infections. CONCLUSION: Aneurysmal bone cysts of the pelvis and sacrum are usually aggressive lesions associated with substantial bone destruction, pathological fractures, and local recurrence. Current management recommendations include preoperative selective arterial embolization, excision-curettage, and bone-grafting.
ENDOSCOPIC CURETTAGE
A new treatment of aneurysmal bone cyst by endoscopic curettage without bone grafting. Otsuka T, Kobayashi M, Sekiya I, Yonezawa M, Kamiyama F, Matsushita Y, Matsui N. Department of Orthopaedic Surgery, Nagoya City University Medical School, Nagoya City, Japan.	Arthroscopy 2001 Sep;17(7):E28 Abstract quote Curettage and bone grafting are the accepted methods of treatment of aneurysmal bone cysts. Unfortunately, recurrence is common. We treated 4 patients with atypical aneurysmal bone cysts that lacked aneurysmal dilatation by endoscopic curettage without bone grafting. New bone formation and remodeling were observed in all patients. In the patients in whom the follow-up was longer than 30 months, there was no evidence of recurrence. Endoscopic curettage without bone grafting is a simple and effective treatment for aneurysmal bone cysts.
RADIATION
Megavoltage radiotherapy for aneurysmal bone cysts. Feigenberg SJ, Marcus RB Jr, Zlotecki RA, Scarborough MT, Berrey BH, Enneking WF. Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL 32610, USA.	Int J Radiat Oncol Biol Phys 2001 Apr 1;49(5):1243-7 Abstract quote PURPOSE: An aneurysmal bone cyst (ABC) is a rapidly expansile and destructive benign tumor of bone that is usually treated by curettage and bone graft, with or without adjuvant treatment. For recurrent tumors, or tumors for which surgery would result in significant functional morbidity, does radiotherapy (RT) provide a safe and effective alternative for local control? PATIENTS AND METHODS: Nine patients with histologically diagnosed aneurysmal bone cysts without other associated benign or malignant tumors were treated at the University of Florida with megavoltage RT between February 1964 and June 1992. The patients received local radiotherapy doses between 20 and 60 Gy, with 6 patients receiving 26--30 Gy. In 6 patients the diagnosis was made by biopsy alone; 3 underwent intralesional curettage before RT. Minimum follow-up was 20 months; 7 of 9 patients (77%) had follow-up greater than 11 years. RESULTS: No patient experienced a local recurrence (median follow-up, 17 years). One patient required stabilization of the cervical spine 10 months after RT because of dorsal kyphosis from vertebral body collapse. No other significant side effects were experienced, and no patients developed secondary malignancies. Four patients were lost to follow-up: at 20 months, 11.5 years, 17 years, and 20 years after the initiation of treatment, none with any evidence of local recurrence. All of the patients who had significant pain before RT had relief of their symptoms within 2 weeks of completion of therapy. CONCLUSIONS: Using modern-day RT, patients with recurrent or inoperable aneurysmal bone cysts can be treated effectively (with minimal toxicity) using a prescribed tumor dose of 26--30 Gy.

EPIDEMIOLOGY	CHARACTERIZATION
SYNONYMS	ABC
AGE RANGE-MEDIAN	First 2 decades
SEX (M:F)	Equal

LABORATORY/RADIOLOGIC/ OTHER TESTS	CHARACTERIZATION
RADIOLOGIC	Eccentric, lytic, and expansile with well-defined margins
X-RAYS
Radiological and clinical features of aneurysmal bone cyst of the jaws. Kaffe I, Naor H, Calderon S, Buchner A. Department of Oral Pathology and Oral Medicine, Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Israel.	Dentomaxillofac Radiol 1999 May;28(3):167-72 Abstract quote PURPOSE: To evaluate the clinical and radiological features of aneurysmal bone cyst (ABC) of the jaws. MATERIALS AND METHODS: A total of 64 cases (60 from the English-language literature and four new cases) were studied and critically evaluated with emphasis on the radiological features. RESULTS: Age at time of initial diagnosis ranged from 4-78 years, with a mean age of 21.5 years and median age of 17 years. There were no differences in gender distribution. The ratio between the mandible and maxilla was 2.4:1. Ninety-two per cent of the lesions were located in the posterior region of the jaws. Lesions were radiolucent in 87% of cases, radiopaque in 2% and mixed in 11%. Fifty-three per cent were multilocular, 43% unilocular and 3% not loculated. The border of the lesions was defined but not corticated in 39%, well defined in 33% and diffuse in 28%. CONCLUSIONS: ABC has a variable radiological appearance and should be considered in the differential diagnosis of any unilocular or multilocular radiolucent lesion of the jaws as well as any mixed radiolucent-radiopaque lesion.
MRI
Imaging of giant cell tumor and giant cell reparative granuloma of bone: radiologic-pathologic correlation. Murphey MD, Nomikos GC, Flemming DJ, Gannon FH, Temple HT, Kransdorf MJ. Department of Radiologic Pathology, Armed Forces Institute of Pathology, 6825 16th St NW, Bldg 54, Rm M-133A, Washington, DC 20306, USA.	Radiographics 2001 Sep-Oct;21(5):1283-309 Abstract quote The radiologic features of giant cell tumor (GCT) and giant cell reparative granuloma (GCRG) of bone often strongly suggest the diagnosis and reflect their pathologic appearance. At radiography, GCT often demonstrates a metaepiphyseal location with extension to subchondral bone. GCRG has a similar appearance but most commonly affects the mandible, maxilla, hands, or feet. Computed tomography and magnetic resonance (MR) imaging are helpful in staging lesions, particularly in delineating soft-tissue extension. Cystic (secondary aneurysmal bone cyst) components are reported in 14% of GCTs. However, biopsy must be directed at the solid regions, which harbor diagnostic tissue. These solid components demonstrate low to intermediate signal intensity at T2-weighted MR imaging, a feature that can be helpful in diagnosis. Multiple GCTs, although rare, do occur and may be associated with Paget disease. Malignant GCT accounts for 5%-10% of all GCTs and is usually secondary to previous irradiation of benign GCT. Treatment of GCT usually consists of surgical resection. Recurrence is seen in 2%-25% of cases, and imaging is vital for early detection. Recognition of the spectrum of radiologic appearances of GCT and GCRG is important in allowing prospective diagnosis, guiding therapy, and facilitating early detection of recurrence.
LABORATORY MARKERS

HISTOLOGICAL TYPES	CHARACTERIZATION
GENERAL	Blood-filled cystic spaces separated by fibrous septa that contain an admixture of fibroblasts, variable numbers of osteoclast-type giant cells, and reactive woven bone.
Aneurysmal bone cyst. A clinicopathologic study of 238 cases. Vergel De Dios AM, Bond JR, Shives TC, McLeod RA, Unni KK. Department of Diagnostic Radiology, Mayo Clinic, Rochester, Minnesota 55905.	Cancer 1992 Jun 15;69(12):2921-31 Abstract quote Aneurysmal bone cyst (ABC) is a nonneoplastic expansile bone lesion that mainly affects children and young adults. Primary ABC is relatively rare, with an incidence one half that of giant cell tumor of bone. In 238 patients with ABC studied in the Mayo Clinic files, more than 80% of the lesions were in long bones, flat bones, or the spinal column. Of the lesions initially treated at the Mayo Clinic, 95% were typical ABC; the rest were "solid" variants. Except for the absence of obvious cavernous channels and spaces, there was no significant histologic difference between solid variant and typical ABC. Radiographically, ABC is an eccentric expansile lesion commonly located at the metaphysis of long bones. Computed tomography and magnetic resonance imaging may show multiple internal septations or fluid levels. In the 153 patients treated, 19% had recurrence after curettage (intralesional excision). Recurrence was most common during the first 2 postoperative years.
VARIANTS

SPECIAL STAINS/IMMUNOPEROXIDASE/ OTHER	CHARACTERIZATION
SPECIAL STAINS
IMMUNOPEROXIDASE
FACTOR VIII
Endothelium in aneurysmal bone cyst. Aho HJ, Aho AJ, Pelliniemi LJ, Ekfors TO, Foidart JM.	Histopathology 1985 Apr;9(4):381-7 Abstract quote The surface of the large cystic spaces and dilated blood vessels in seven cases of aneurysmal bone cysts was studied. The endothelium of the blood vessels was surrounded by a layer of collagen types IV and V, and the endothelial cells contained factor VIII related antigen demonstrated by the peroxidase anti-peroxidase technique. Some blood vessels were dilated resembling small aneurysmal spaces. The visible surfaces of the aneurysmal spaces were devoid of collagen types IV and V, and of factor VIII related antigen. Ultrastructural analysis of paraffin embedded sections did not show the characteristic fine structural features of endothelium covering the aneurysmal spaces. It is concluded that the large spaces in aneurysmal bone cysts are devoid of basement membranes and endothelial cells. The absence of endothelium may explain the abundance of haemorrhages in these lesions. Immunocytochemical demonstration of endothelial antigen provides a valuable tool for the differential diagnosis between aneurysmal bone cysts and vascular tumours.