Lipoblastoma

Background

This rare soft tissue tumor commonly presents in the neonatal period. It is benign but may rarely recur. The pathologist must distinguish this benign tumor from the malignant liposarcoma.

OUTLINE

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

Internet Links

PATHOGENESIS CHARACTERIZATION

CHROMOSOMAL ABNORMALITIES

Evidence by spectral karyotyping that 8q11.2 is nonrandomly involved in lipoblastoma.

Chen Z, Coffin CM, Scott S, Meloni-Ehrig A, Shepard R, Issa B, Forsyth DR, Sandberg AA, Brothman AR, Lowichik A.

Cytogenetics Laboratory, University of Utah School of Medicine, Salt Lake City 84132, USA.
J Mol Diagn 2000 May;2(2):73-7 Abstract quote
We report two cases of lipoblastoma with chromosome 8-related aberrations, ie, a 92,XXYY,t(7;8Xp22;q11.2)x2 [8]/46,XY[16] in Case 1 and a 46,XY,-8,-13,add(16) (q22),+mar, +r [cp13]/46,XY[7] in Case 2.

Using spectral karyotyping and fluorescence in situ hybridization techniques, the karyotype of Case 2 was redesignated as 46,XY, r(8), del(13)(q12), der(16)ins(16;8)(q22; q24q11.2)[cp13]/46,XY[7]. This report delineates a new chromosome rearrangement, ie, der(16)ins(16;8)(q22; q24q11.2) in lipoblastoma, and also confirms the t(7; 8)(p22;q11.2), reported only once previously, as a recurrent translocation involved in such a tumor.

These findings provide valuable information for clinical molecular cytogenetic diagnosis of lipoblastoma. Furthermore, this report highlights the value of cytogenetic and molecular cytogenetic analysis in differential diagnosis of childhood adipose tissue tumors and adds to the number of lipoblastomas reported with chromosomal abnormalities at 8q11.2.

Case of lipoblastoma with two derivative chromosomes 8 containing homogeneously staining-like regions and a review of the literature: lipoblastoma and chromosome 8.

Batanian JR, Brink DS, Thorpe CM, Haddad BR.

Department of Pediatrics, St. Louis School of Medicine, Pediatric Research Institute, Cardinal Glennon Children's Hospital, St. Louis, MO, USA.
Cancer Genet Cytogenet 2001 Feb;125(1):10-3 Abstract quote
We report a case of a lipoblastoma in a 10-month-old girl in which the cytogenetic aberration showed a homogeneously staining-like region (hsr) within two derivative chromosomes 8.

There was a loss of one normal copy of chromosome 8 and gain of two identical derivative chromosomes 8 with the karyotype designation 47,XX,psu idic(8)(pter-->q12 approximately 13::hsr::q12 approximately 13-->pter),+psu idic (8)(pter-->q12 approximately 13::hsr::q12 approximately 13-->pter).

This is the first report of a chromosomal aberration of this type seen in lipoblastoma.

ONCOGENES

PLAG1 alterations in lipoblastoma: involvement in varied mesenchymal cell types and evidence for alternative oncogenic mechanisms.

Gisselsson D, Hibbard MK, Dal Cin P, Sciot R, Hsi BL, Kozakewich HP, Fletcher JA.

Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.

Am J Pathol 2001 Sep;159(3):955-62 Abstract quote
Lipoblastomas are rare soft tissue tumors that occur primarily in young children. They typically contain variably differentiated adipocytes, primitive mesenchymal cells, myxoid matrix, and fibrous trabeculae.

Abnormalities in chromosome 8, leading to rearrangements of the PLAG1 gene, were demonstrated recently in four lipoblastomas. In the present report, we determine the frequency of PLAG1 alterations in 16 lipoblastomas from children aged 13 years or younger, and we also evaluate the stages of lipoblastoma differentiation at which PLAG1 genomic alterations are found. Eleven lipoblastomas (69%), including those with either classic or lipoma-like histology, had rearrangements of the 8q12 PLAG1 region. Another three lipoblastomas had polysomy for chromosome 8 in the absence of PLAG1 rearrangement. Only two cases (13%) lacked a chromosome 8 abnormality. Notably, the lipoblastomas with chromosome 8 polysomy had up to five copies of chromosome 8 as an isolated cytogenetic finding in an otherwise diploid cell.

We also demonstrate that PLAG1 alterations are found in a spectrum of mesenchymal cell types in lipoblastomas, including lipoblasts, mature adipocytes, primitive mesenchymal cells, and fibroblast-like cells. This finding is consistent with neoplastic origin in a primitive mesenchymal precursor and with variable differentiation to a mature adipocyte end-point.

Hence, our studies provide biological validation for the clinical observation that lipoblastomas can evolve into mature, lipoma-like, lesions. They also suggest that PLAG1 dosage alterations caused by polysomy 8 might represent an alternative oncogenic mechanism in lipoblastoma.

LABORATORY/
RADIOLOGIC/
OTHER TESTS
CHARACTERIZATION

RADIOLOGIC

Shoulder lipoblastoma: magnetic resonance imaging characteristics.

Letourneau L, Dufour M, Deschenes J.

Departement de radiologie, Hopital Laval, Sainte-Foy, Que.

Can Assoc Radiol J 1993 Jun;44(3):211-4 Abstract quote
The authors describe the magnetic resonance imaging (MRI) characteristics of lipoblastoma of the shoulder in an infant. The appearance of the lesion in MRI scans correlated well with the pathological observation of lobules of immature adipose tissue surrounding masses of myxoid tissue.

However, the MRI study of lipoblastoma is nonspecific, and the results of other radiologic modalities, such as plain radiography, ultrasonography and computed tomography, are essential for a confident diagnosis.

GROSS APPEARANCE/
CLINICAL VARIANTS CHARACTERIZATION

GENERAL

VARIANTS

ADULT

Benign recurring lipoblastoma in an adult versus well differentiated subcutaneous myxoid liposarcoma: clinicopathologic, immunohistochemical and molecular analysis of a unique case.

Silverman JS, Hamilton J, Tamsen A.

Department of Pathology, Southampton Hospital, New York 11937, USA.
Pathol Res Pract 1999;195(11):787-92; discussion 793 Abstract quote
Subcutaneous myxoid liposarcoma (ML) is exceedingly rare, with only two or three cases having been reported. Lipoblastoma (LB), a rare fatty tumor that arises in infants and children, is unknown after adolescence. In contrast to ML, LB is often superficial. The two tumors can be difficult to distinguish due to many histologic similarities.

We examined a 0.9 cm superficial subcutaneous nodule from the dorsal neck of a 48 year old man that had been growing slowly. Three and one half years later, a 0.4 cm palpable recurrent nodule was excised from the scar. The patient is now free of disease at 7.5 years. Because of these unusual features, we performed clinicopathologic, immunohistochemical and molecular analysis of this unusual tumor to decide if this represented a rare cutaneous ML or an unprecedented example of LB in an adult.

The primary featured a thick fibrous pseudocapsule with foci of lymphocytes and infiltrating nests of semi-mature fetal-appearing adipocytic tissue. This surrounded a more immature cellular-but-cytologically-bland myxoid tissue featuring stellate cells and signet lipoblasts. There were fibrous sep at the periphery and the vasculature was rather inconspicuous. The 0.4 cm diameter recurrence was distinctly lobular and had minute satellite nodules. It was composed of uniform fetal-appearing bland myxoid lipoblastic tissue featuring signet ring lipoblasts surrounded by a few spindle cells. In both tumors, lipoblasts expressed S-100 protein. In the primary, 5% of the lesional cells were FXIIIa+ dendritic stromal histiocytes while in the recurrence, 15% of the lesional cells were FXIIIa+ dendritic cells. CD34 stained only scattered small capillaries. The Ki67 proliferation index was 1% in the primary and 3% in the recurrence. RT-PCR assay for TLS/FUS-CHOP fusion transcripts was negative despite three repeat tests performed on paraffin sections of the primary tumor in the presence of good m-RNA internal controls.

We reviewed the clinicopathologic and cytogenetic features of ML and LB. Based on this review and on the growth pattern, anatomic features and molecular data from the present case, we conclude that this tumor may represent the first reported case of adult LB.

HEART

Primary cardiac lipoblastoma.

Dishop MK, O'Connor WN, Abraham S, Cottrill CM.

Department of Pathology and Laboratory Medicine, University of Kentucky Medical Center, MS 117, Lexington, KY 40536, USA.
Pediatr Dev Pathol 2001 May-Jun;4(3):276-80 Abstract quote
Lipoblastoma is a benign adipose tumor in children that has been described in various anatomic locations, most commonly the extremities.

We describe the case of a 17-month-old boy diagnosed with cardiac lipoblastoma, a previously unreported primary cardiac tumor in children. Our patient presented with symptoms of coughing, wheezing, and hoarseness and was found to have a large mediastinal mass, which narrowed the left mainstem bronchus and compressed the right atrium and superior vena cava, causing superior vena cava syndrome. Surgical exploration revealed an intrapericardial soft tissue mass arising from the area of the posterior interatrial septum. Grossly, the resected mass was lobulated, pale yellow, and fatty with focal areas of gray myxoid tissue.

Microscopically, the tumor consisted of both immature and mature adipocytes, with focal vascular myxoid areas containing lipoblasts, diagnostic of lipoblastoma. Two months after surgery, the patient was in good health without evidence of recurrence.

MEDIASTINUM, POSTERIOR

An unusual posterior mediastinal lipoblastoma with spinal epidural extension presenting as a painful suprascapular swelling: case report and a brief review of the literature.

Raman Sharma R, Mahapatra AK, Pawar SJ, Sousa J, Musa MM.

Senior Specialist in Neurosurgery, Neurosurgery, National Neurosurgical Center, Khoula Hospital, Muscat, Sultanate of Oman
J Clin Neurosci 2002 Mar;9(2):204-7 Abstract quote
Lipoblastoma is a rare benign pediatric neoplasm of fetal-embryonal fat with little risk of recurrence following total microsurgical excision, but it may progress to local invasion or infiltration ifnot treated surgically. No adjuvant therapies are usually necessary once the tumor is excised. It is best diagnosed on histopathological studiesfollowing excision.

An unusual posterior mediastinal lipoblastoma in a 2-year-old Omani girl with spinal epidural extension clinically manifested as a progressive painful suprascapular swelling is reported. It was initially construed to be a benign lipoma, but progressively increasing pain and mild imbalance whilst walking with a tendency to fall on the right side prompted neurosurgical referral and eventual total excision without any added morbidity. Interesting clinical and neuroimaging (CT & MRI) findings are presented and discussed, with a brief review of the literature.

SCROTAL

Intrascrotal lipoblastoma with a complex karyotype: a case report and review of the literature.

Somers GR, Teshima I, Nasr A, Cook A, Khoury AE, Taylor GP.

Division of Pathology, Hospital for Sick Children, Toronto, Ontario, Canada.

Arch Pathol Lab Med. 2004 Jul;128(7):797-800. Abstract quote

Lipoblastoma is a tumor of adipose tissue that usually occurs in young children. Most lipoblastomas occur on the extremities, trunk, and head and neck, and most have rearrangements of the 8q region.

We describe a lipoblastoma in a 12-month-old boy who presented with a rapidly enlarging scrotal mass. Electron microscopy revealed features consistent with immature adipocytes, and cytogenetic analysis revealed the following karyotype: 57,XY,+4,+6,+7,der(8)t(8;12) (q22;q13), +der(8)t(8;12) (q22;q13), +9,+10,+12,-16,+17,+der(18)t(8;18)(q22;q23),+19,+20. Interestingly, the breakpoint on chromosome 12 (q13) is the same as that seen in lipoblastomas.

To our knowledge, this is the first reported case of such a complex karyotype in lipoblastoma and adds to the expanding list of karyotypic abnormalities seen in such tumors.

SKIN

Congenital palpebral lipoblastoma. First report of a case.

Enghardt MH, Warren RC.

Department of Pathology, Brooke Army Medical Center, San Antonio, TX 78234.
Am J Dermatopathol 1990 Aug;12(4):408-11 Abstract quote
Lipoblastoma, an uncommon benign tumor of adipose tissue, occurs in infants and young children. Anatomic sites usually involved include extremities, neck, trunk, retroperitoneum, and mediastinum.

To our knowledge, no cases involving the eyelids have previously been reported. Its clinical presentation and appearance are not distinctive; diagnosis and differentiation from other lipocytic tumors are achieved via routine light-microscopic studies. Lipoblastoma is composed of fat cells exhibiting a broad spectrum of differentiation. Simple excision suffices as treatment.

HISTOLOGICAL TYPES CHARACTERIZATION

GENERAL

Lipoblastoma and lipoblastomatosis: a clinicopathological study of 14 cases.

Mentzel T, Calonje E, Fletcher CD.

Department of Histopathology, St Thomas's Hospital (U.M.D.S.), London, UK.
Histopathology 1993 Dec;23(6):527-33 Abstract quote
The clinicopathological features of 14 cases of lipoblastoma and lipoblastomatosis are presented. The age of the patients at presentation ranged from 5 days to 6 years (mean 2.7 years); nine patients were male.

Histologically, six cases were circumscribed (lipoblastoma) while eight were diffuse and ill-defined (lipoblastomatosis). In both groups and in individual cases there was distinct lobulation, as well as a spectrum of adipocytic maturation.

Cytologically, the 10 most mature lesions were composed of uniform adipocytes intermixed with only scattered lipoblasts and primitive mesenchymal cells. A notable feature in the other four cases was a prominent myxoid stroma producing a very close resemblance to myxoid liposarcoma. Mitotic figures were rare and always normal in appearance. Atypical nuclei were not evident.

Follow-up in eight patients revealed local recurrence in two. Liposarcoma in patients under 10 years is exceedingly rare, and, in myxoid form, may be almost impossible to distinguish histologically from lipoblastoma. Helpful clues are the lack of lobulation, variable growth pattern and increased nuclear atypia in liposarcoma.

Lipoblastoma/lipoblastomatosis: a clinicopathologic study of 25 tumors.

Collins MH, Chatten J.

Department of Pathology, The Children's Hospital of Philadelphia, Pennsylvania 19104, USA.
Am J Surg Pathol 1997 Oct;21(10):1131-7 Abstract quote
Lipoblastoma/lipoblastomatosis is an uncommon benign adipose tissue tumor of children. Since 1958, 25 of these tumors from 24 patients have been reviewed in the Department of Pathology at The Children's Hospital of Philadelphia. Tumors were resected from 19 boys (79%) and five girls, and 20 patients (84%) were < or =5 years of age at diagnosis.

Twenty-three tumors presented as painless superficial soft-tissue masses; one tumor was retroperitoneal and was discovered because of vomiting; one hand tumor was present at birth. Tumors occurred in an extremity (n = 11 patients), the head and neck (n = 5), groin (n = 2), axilla (n = 2), back (n = 1), chest (n = 1), flank (n = 1), labia (n = 1), and retroperitoneum (n = 1). Thirteen tumors occurred on the left side, and five occurred on the right. Lesions measured 1.0-21.0 cm in greatest dimension; 15 of 25 (60%) measured < or =5.0 cm. The largest (retroperitoneal) tumor weighed 450 g. Eleven tumors were discrete lipoblastoma, and 14 had irregular margins (lipoblastomatosis). Microscopically, the tumors displayed adipocytes in different stages of maturation; lobules bordered by septae that were cellular in 11 cases; prominent blood vessels in 19 cases; and myxoid foci in 13 cases. Chart review of 22 patients showed that one tumor recurred 4 years after resection; one tumor recurred after 7 years as fibrolipoma; and one incompletely resected tumor enlarged and at second resection was lipoma. There were no metastases. Three patients also had hemangioma. Juvenile aponeurotic fibroma occurred in one patient near the site of resection of a lipoblastoma 4 years earlier.

We conclude that lipoblastoma/lipoblastomatosis behaves benignly, occurs in both superficial and deep sites, occasionally attains large size, may mature, can recur, and may be associated with other benign soft-tissue lesions. Complete surgical excision is the treatment of choice.

SPECIAL STAINS/
IMMUNOPEROXIDASE/
OTHER CHARACTERIZATION

SPECIAL STAINS

IMMUNOPEROXIDASE

ELECTRON MICROSCOPY

Lipoblastoma and lipoblastomatosis in infancy and childhood: histopathologic, ultrastructural, and cytogenetic features.

Hicks J, Dilley A, Patel D, Barrish J, Zhu SH, Brandt M.

Department of Pathology, Texas Children's Hospital and Baylor College of Medicine, Houston 77030-2399, USA.
Ultrastruct Pathol 2001 Jul-Aug;25(4):321-33 Abstract quote
Lipoblastoma is a relatively rare tumor that occurs in infancy and early childhood and arises from embryonic white fat. Although a benign tumor, lipoblastomas tend to recur and may resemble myxoid liposarcoma.

The authors report 26 cases over a 15-year period at Texas Children's Hospital. There was a slight female predilection (14F:12M). The most common symptom was a painless mass with or without increasing size. The trunk, extremities, head and neck, retroperitoneum, inguinal canal, peritoneal cavity, and lung were the tumor sites. Most tumors were circumscribed lipoblastomas and the minority were diffuse infiltrative lipoblastomatosis. Reexcision for residual or recurrent tumor was necessary more frequently in patients with lipoblastomatosis. Histopathologic examination and ultrastructural examination revealed cellular neoplasms composed of immature adipocytes with relatively well-defined septa, frequent lipoblasts, a fine vascular network, and often a myxoid appearance resembling myxoid liposarcoma. Cytogenetics was performed in 4 cases with chromosome 8q abnormality being most common.

The major concern with lipoblastoma in children is to completely excise the tumor to avoid leaving residual tumor and to prevent recurrences. Confusion with myxoid liposarcoma, well-differentiated liposarcoma, and typical lipomas may occur. Although asymptomatic, lipoblastomas may cause dysfunction of other organ systems due to mass effect. Complete surgical excision with at least 2 years of follow-up is the preferred therapy.

DIFFERENTIAL DIAGNOSIS KEY DIFFERENTIATING FEATURES

LIPOMA

LIPOSARCOMA

Benign lipoblastoma and myxoid liposarcoma: a comparative light- and electron-microscopic study.

Bolen JW, Thorning D.

Am J Surg Pathol 1980 Apr;4(2):163-74 Abstract quote
A benign lipoblastoma and a myxoid liposarcoma were studied by light and electron microscopy. Both of these neoplasms had prominent plexiform vascular networks, early acquisition of fat by vascular pericytes, and progressive accumulation of fat by cells located away from the vasculature. Their component cells had investing basal laminae, pinocytotic vesicles, and cytoplasmic glycogen stores as well as cytoplasmic lipid. The process of neoplastic lipogenesis and the structural features of the neoplastic cells in both neoplasms resembled those of developing non-neoplastic fat tissue.

The benign lipoblastoma appears to be analogous to developing fat, while the myxoid liposarcoma appears to recapitulate the actively proliferating zone of developing fat. The relationship between proliferating cells and the plexiform vascular network in all three processes is emphasized. We hypothesize that the vascular pericyte serves as a source for new fat storing cells.

Lipoblastoma and liposarcoma in children: an analysis of 9 cases and a review of the literature.

Miller GG, Yanchar NL, Magee JF, Blair GK.

Department of Surgery, University of British Columbia, British Columbia's Children's Hospital, Vancouver.
Can J Surg 1998 Dec;41(6):455-8 Abstract quote
OBJECTIVES: To review the experience at a children's hospital of lipoblastoma and liposarcoma and to identify any factors that would differentiate one type of tumour from the other.

DESIGN: A retrospective case series.

SETTING: British Columbia's Children's Hospital a tertiary-care pediatric centre.

PATIENTS: All patients with a pathological diagnosis of lipoblastoma and liposarcoma recorded over 12 years.

MAIN OUTCOME MEASURES: The frequency of lipoblastoma and liposarcoma, identified from biopsy specimens of pediatric adipose tumours. The clinical, pathological and cytogenetic variables between lipoblastoma and liposarcoma.

RESULTS: One hundred and forty-nine adipose tumours were recorded. Seven (4.7%) were lipoblastomas and 2 (1.3%) were liposarcomas. All tumours presented as asymptomatic, slow-growing, soft-tissue masses. The children with lipoblastoma tended to be younger, but 29% were over 3 years of age. The liposarcoma patients were aged 9 and 14 years. One liposarcoma was of myxoid type and the other was a round cell variant. Karyotypes were reported for 1 lipoblastoma and 1 liposarcoma. The myxoid liposarcoma karyotype was 46,XY,t(12;16)(q13;p11), and the lipoblastoma was reported as 46,XY,der(8)?t(8q;?),+mar.

CONCLUSIONS: Lipoblastoma is an unusual childhood neoplasm and liposarcoma is very rare in children. Both tumours may present in a similar fashion, and differentiating them histologically can be difficult. Age cannot be relied upon to accurately predict their behaviour. The tumour karyotype is very helpful in differentiating these neoplasms.

PROGNOSIS AND TREATMENT CHARACTERIZATION

PROGNOSTIC FACTORS

GENERAL

Lipoblastoma in infancy and childhood.

Jimenez JF.
J Surg Oncol 1986 Aug;32(4):238-44 Abstract quote
Lipoblastoma is a rare benign neoplasm of fetal-embryonal fat tissue with a 14% tendency to recur. It occurs almost exclusively in infants and children.

To my knowledge, less than 100 cases, including children and adults, have been reported in the English literature. Two retroperitoneal and one case of mesenteric lipoblastoma, all presenting as a large palpable abdominal mass, are described.

Our patients, aged 12 years, 7 months, and 11 months, were treated by total surgical excision of the tumors. They are alive and well 5, 4, and 3 years postoperative, respectively, with no evidence of recurrence and no indication for any adjunctive therapy. Pathologic evaluation was decisive for the best treatment and prognosis.

Lipoblastoma: better termed infantile lipoma?

O'Donnell KA, Caty MG, Allen JE, Fisher JE.

Department of Surgery, State University of New York at Buffalo School of Medicine and Biomedical Sciences, USA.
Pediatr Surg Int 2000;16(5-6):458-61 Abstract quote
Lipoblastoma is a rare adipose tumor occurring exclusively in childhood. There have been no reports of metastases, making the designation "blastoma" confusing, since this term is usually reserved for malignant tumors.

Two recent cases treated at our institution confirm its benign nature. In addition, a review of the literature supports the idea that the tumor may more accurately be described as an "infantile lipoma". Infantile lipoma better reflects many of the tumor's characteristics such as, its early occurrence, it's ability to mature into a simple lipoma, it's cellular composition of mainly mature adipocytes, and its benign course.

Although lipoblastoma is an uncommonly encountered tumor, making an effort to change its name to infantile lipoma will result in a more a accurate term that will facilitate treatment.

Lipoblastoma.

Chun YS, Kim WK, Park KW, Lee SC, Jung SE.

Department of Pediatric Surgery, Seoul National University Children's Hospital, Chongno-gu, Korea.
J Pediatr Surg 2001 Jun;36(6):905-7 Abstract quote
BACKGROUND/PURPOSE: Lipoblastoma is a rare benign mesenchymal tumor of embryonal fat that occurs almost exclusively in infants and children. This study was done to determine the clinical and pathologic characteristics of lipoblastoma.

METHODS: Nine cases of pathologically proven lipoblastoma from 1979 to 1997 were reviewed. There were 6 boys and 3 girls ranging in age from 3 months to 29 months.

RESULTS: A soft tissue mass was the chief complaint in 7 patients, abdominal distension in 1 patient with a retroperitoneal mass, and defecation difficulty in 1 patient with a perirectal mass. In 4 patients, tumors occurred on the back. Other tumor location includes the neck, scrotum, retroperitoneum, perirectal area, and buttock in 1 patient each. Lesions measured 2.3 to 19.5 cm. Complete excision was done in 8 patients. One perirectal tumor was removed by both the posterior sagittal approach and the intraabdominal approach but incompletely resected. Two tumors located on the back recurred with intraspinal extension 12 months and 18 months after resection. Second resection and second resection with laminectomy were done. Leg pain and urinary incontinence developed in 1 patient but improved on conservative treatment.

CONCLUSIONS: Lipoblastoma is a benign neoplasm but can frequently recur (25%) in spite of complete excision. Lipoblastomas occurring on the back had a high recurrence rate (50%) and associated with intraspinal extension.

TREATMENT

SURGERY

Is surgical treatment of lipoblastoma always necessary?

Mognato G, Cecchetto G, Carli M, Talenti E, d'Amore ES, Pederzini F, Guglielmi M.

Department of Pediatrics, University of Padua, Italy.
J Pediatr Surg 2000 Oct;35(10):1511-3 Abstract quote
Lipoblastoma is an uncommon, benign mesenchymal tumor with an excellent prognosis despite its potential to local invasion and rapid growth. However, in the literature, a spontaneous resolution has never been reported, and, consequently, the need for a complete surgical excision has never been questioned.

The authors report a case of a 2-day-old boy with congenital diffuse lipoblastoma in the left thigh, which forced us to withhold from surgical treatment to avoid the risk of mutilation in a patient so young. The lesion was followed-up by imaging, and a complete spontaneous resolution of the diffuse lipoblastoma was shown by magnetic resonance imaging (MRI) at 1-year follow-up. In the literature, a complete surgical excision is recommended.

The results of this case suggest that a "wait and see" approach is justified at least in infants with huge invasive lesions requiring a mutilating excision.

Lipoblastoma: pathophysiology and surgical management.

Dilley AV, Patel DL, Hicks MJ, Brandt ML.

Department of Surgery, Baylor College of Medicine, Houston, TX 77030, USA.
J Pediatr Surg 2001 Jan;36(1):229-31 Abstract quote
BACKGROUND/PURPOSE: Lipoblastoma/lipoblastomatosis is a poorly understood and uncommon soft tissue tumor of infancy and early childhood. Twenty-four patients that presented to a single institution over a 15-year period were reviewed for clinical features and outcome.

METHODS: A retrospective review was conducted.

RESULTS: Twenty-five cases were identified; 1 chart was not available for review. Fourteen girls and 11 boys with a median age of 20 months (2 months, 10 years) presented with 26 separate tumors. Nineteen were focal and 7 diffuse. The tumors were located on the trunk (n = 13), leg (n = 6), arm (n = 3), and head and neck (n = 4). Five patients (all with diffuse type) had up to 3 recurrences.

CONCLUSIONS: Patients with focal lipoblastoma are unlikely to require further surgery after initial resection. Patients with diffuse lipoblastoma (lipoblastomatosis) are likely to have recurrent disease (usually within 2 years) and should undergo close follow-up. Genetic analysis of the specimen will help exclude liposarcoma. Recurrent lesions are best imaged with magnetic resonance imaging to assess extent and plan reconstruction if necessary.

Rosai J. Ackerman's Surgical Pathology. Eight Edition. Mosby 1996.
Sternberg S. Diagnostic Surgical Pathology. Third Edition. Lipincott Williams and Wilkins 1999.
Weedon D. Weedon's Skin Pathology. Churchill Livingstone. 1997.
Fitzpatrick's Dermatology in General Medicine. 5th Edition. McGraw-Hill. 1999.
Robbins Pathologic Basis of Disease. Sixth Edition. WB Saunders 1999.
Weiss SW and Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors. Fourth Edition. Mosby 2001.

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Last Updated 7/1/2004

PATHOGENESIS	CHARACTERIZATION
CHROMOSOMAL ABNORMALITIES
Evidence by spectral karyotyping that 8q11.2 is nonrandomly involved in lipoblastoma. Chen Z, Coffin CM, Scott S, Meloni-Ehrig A, Shepard R, Issa B, Forsyth DR, Sandberg AA, Brothman AR, Lowichik A. Cytogenetics Laboratory, University of Utah School of Medicine, Salt Lake City 84132, USA.	J Mol Diagn 2000 May;2(2):73-7 Abstract quote We report two cases of lipoblastoma with chromosome 8-related aberrations, ie, a 92,XXYY,t(7;8Xp22;q11.2)x2 [8]/46,XY[16] in Case 1 and a 46,XY,-8,-13,add(16) (q22),+mar, +r [cp13]/46,XY[7] in Case 2. Using spectral karyotyping and fluorescence in situ hybridization techniques, the karyotype of Case 2 was redesignated as 46,XY, r(8), del(13)(q12), der(16)ins(16;8)(q22; q24q11.2)[cp13]/46,XY[7]. This report delineates a new chromosome rearrangement, ie, der(16)ins(16;8)(q22; q24q11.2) in lipoblastoma, and also confirms the t(7; 8)(p22;q11.2), reported only once previously, as a recurrent translocation involved in such a tumor. These findings provide valuable information for clinical molecular cytogenetic diagnosis of lipoblastoma. Furthermore, this report highlights the value of cytogenetic and molecular cytogenetic analysis in differential diagnosis of childhood adipose tissue tumors and adds to the number of lipoblastomas reported with chromosomal abnormalities at 8q11.2.
Case of lipoblastoma with two derivative chromosomes 8 containing homogeneously staining-like regions and a review of the literature: lipoblastoma and chromosome 8. Batanian JR, Brink DS, Thorpe CM, Haddad BR. Department of Pediatrics, St. Louis School of Medicine, Pediatric Research Institute, Cardinal Glennon Children's Hospital, St. Louis, MO, USA.	Cancer Genet Cytogenet 2001 Feb;125(1):10-3 Abstract quote We report a case of a lipoblastoma in a 10-month-old girl in which the cytogenetic aberration showed a homogeneously staining-like region (hsr) within two derivative chromosomes 8. There was a loss of one normal copy of chromosome 8 and gain of two identical derivative chromosomes 8 with the karyotype designation 47,XX,psu idic(8)(pter-->q12 approximately 13::hsr::q12 approximately 13-->pter),+psu idic (8)(pter-->q12 approximately 13::hsr::q12 approximately 13-->pter). This is the first report of a chromosomal aberration of this type seen in lipoblastoma.
ONCOGENES
PLAG1 alterations in lipoblastoma: involvement in varied mesenchymal cell types and evidence for alternative oncogenic mechanisms. Gisselsson D, Hibbard MK, Dal Cin P, Sciot R, Hsi BL, Kozakewich HP, Fletcher JA. Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.	Am J Pathol 2001 Sep;159(3):955-62 Abstract quote Lipoblastomas are rare soft tissue tumors that occur primarily in young children. They typically contain variably differentiated adipocytes, primitive mesenchymal cells, myxoid matrix, and fibrous trabeculae. Abnormalities in chromosome 8, leading to rearrangements of the PLAG1 gene, were demonstrated recently in four lipoblastomas. In the present report, we determine the frequency of PLAG1 alterations in 16 lipoblastomas from children aged 13 years or younger, and we also evaluate the stages of lipoblastoma differentiation at which PLAG1 genomic alterations are found. Eleven lipoblastomas (69%), including those with either classic or lipoma-like histology, had rearrangements of the 8q12 PLAG1 region. Another three lipoblastomas had polysomy for chromosome 8 in the absence of PLAG1 rearrangement. Only two cases (13%) lacked a chromosome 8 abnormality. Notably, the lipoblastomas with chromosome 8 polysomy had up to five copies of chromosome 8 as an isolated cytogenetic finding in an otherwise diploid cell. We also demonstrate that PLAG1 alterations are found in a spectrum of mesenchymal cell types in lipoblastomas, including lipoblasts, mature adipocytes, primitive mesenchymal cells, and fibroblast-like cells. This finding is consistent with neoplastic origin in a primitive mesenchymal precursor and with variable differentiation to a mature adipocyte end-point. Hence, our studies provide biological validation for the clinical observation that lipoblastomas can evolve into mature, lipoma-like, lesions. They also suggest that PLAG1 dosage alterations caused by polysomy 8 might represent an alternative oncogenic mechanism in lipoblastoma.

HISTOLOGICAL TYPES	CHARACTERIZATION
GENERAL
Lipoblastoma and lipoblastomatosis: a clinicopathological study of 14 cases. Mentzel T, Calonje E, Fletcher CD. Department of Histopathology, St Thomas's Hospital (U.M.D.S.), London, UK.	Histopathology 1993 Dec;23(6):527-33 Abstract quote The clinicopathological features of 14 cases of lipoblastoma and lipoblastomatosis are presented. The age of the patients at presentation ranged from 5 days to 6 years (mean 2.7 years); nine patients were male. Histologically, six cases were circumscribed (lipoblastoma) while eight were diffuse and ill-defined (lipoblastomatosis). In both groups and in individual cases there was distinct lobulation, as well as a spectrum of adipocytic maturation. Cytologically, the 10 most mature lesions were composed of uniform adipocytes intermixed with only scattered lipoblasts and primitive mesenchymal cells. A notable feature in the other four cases was a prominent myxoid stroma producing a very close resemblance to myxoid liposarcoma. Mitotic figures were rare and always normal in appearance. Atypical nuclei were not evident. Follow-up in eight patients revealed local recurrence in two. Liposarcoma in patients under 10 years is exceedingly rare, and, in myxoid form, may be almost impossible to distinguish histologically from lipoblastoma. Helpful clues are the lack of lobulation, variable growth pattern and increased nuclear atypia in liposarcoma.
Lipoblastoma/lipoblastomatosis: a clinicopathologic study of 25 tumors. Collins MH, Chatten J. Department of Pathology, The Children's Hospital of Philadelphia, Pennsylvania 19104, USA.	Am J Surg Pathol 1997 Oct;21(10):1131-7 Abstract quote Lipoblastoma/lipoblastomatosis is an uncommon benign adipose tissue tumor of children. Since 1958, 25 of these tumors from 24 patients have been reviewed in the Department of Pathology at The Children's Hospital of Philadelphia. Tumors were resected from 19 boys (79%) and five girls, and 20 patients (84%) were < or =5 years of age at diagnosis. Twenty-three tumors presented as painless superficial soft-tissue masses; one tumor was retroperitoneal and was discovered because of vomiting; one hand tumor was present at birth. Tumors occurred in an extremity (n = 11 patients), the head and neck (n = 5), groin (n = 2), axilla (n = 2), back (n = 1), chest (n = 1), flank (n = 1), labia (n = 1), and retroperitoneum (n = 1). Thirteen tumors occurred on the left side, and five occurred on the right. Lesions measured 1.0-21.0 cm in greatest dimension; 15 of 25 (60%) measured < or =5.0 cm. The largest (retroperitoneal) tumor weighed 450 g. Eleven tumors were discrete lipoblastoma, and 14 had irregular margins (lipoblastomatosis). Microscopically, the tumors displayed adipocytes in different stages of maturation; lobules bordered by septae that were cellular in 11 cases; prominent blood vessels in 19 cases; and myxoid foci in 13 cases. Chart review of 22 patients showed that one tumor recurred 4 years after resection; one tumor recurred after 7 years as fibrolipoma; and one incompletely resected tumor enlarged and at second resection was lipoma. There were no metastases. Three patients also had hemangioma. Juvenile aponeurotic fibroma occurred in one patient near the site of resection of a lipoblastoma 4 years earlier. We conclude that lipoblastoma/lipoblastomatosis behaves benignly, occurs in both superficial and deep sites, occasionally attains large size, may mature, can recur, and may be associated with other benign soft-tissue lesions. Complete surgical excision is the treatment of choice.

PROGNOSIS AND TREATMENT	CHARACTERIZATION
PROGNOSTIC FACTORS
GENERAL
Lipoblastoma in infancy and childhood. Jimenez JF.	J Surg Oncol 1986 Aug;32(4):238-44 Abstract quote Lipoblastoma is a rare benign neoplasm of fetal-embryonal fat tissue with a 14% tendency to recur. It occurs almost exclusively in infants and children. To my knowledge, less than 100 cases, including children and adults, have been reported in the English literature. Two retroperitoneal and one case of mesenteric lipoblastoma, all presenting as a large palpable abdominal mass, are described. Our patients, aged 12 years, 7 months, and 11 months, were treated by total surgical excision of the tumors. They are alive and well 5, 4, and 3 years postoperative, respectively, with no evidence of recurrence and no indication for any adjunctive therapy. Pathologic evaluation was decisive for the best treatment and prognosis.
Lipoblastoma: better termed infantile lipoma? O'Donnell KA, Caty MG, Allen JE, Fisher JE. Department of Surgery, State University of New York at Buffalo School of Medicine and Biomedical Sciences, USA.	Pediatr Surg Int 2000;16(5-6):458-61 Abstract quote Lipoblastoma is a rare adipose tumor occurring exclusively in childhood. There have been no reports of metastases, making the designation "blastoma" confusing, since this term is usually reserved for malignant tumors. Two recent cases treated at our institution confirm its benign nature. In addition, a review of the literature supports the idea that the tumor may more accurately be described as an "infantile lipoma". Infantile lipoma better reflects many of the tumor's characteristics such as, its early occurrence, it's ability to mature into a simple lipoma, it's cellular composition of mainly mature adipocytes, and its benign course. Although lipoblastoma is an uncommonly encountered tumor, making an effort to change its name to infantile lipoma will result in a more a accurate term that will facilitate treatment.
Lipoblastoma. Chun YS, Kim WK, Park KW, Lee SC, Jung SE. Department of Pediatric Surgery, Seoul National University Children's Hospital, Chongno-gu, Korea.	J Pediatr Surg 2001 Jun;36(6):905-7 Abstract quote BACKGROUND/PURPOSE: Lipoblastoma is a rare benign mesenchymal tumor of embryonal fat that occurs almost exclusively in infants and children. This study was done to determine the clinical and pathologic characteristics of lipoblastoma. METHODS: Nine cases of pathologically proven lipoblastoma from 1979 to 1997 were reviewed. There were 6 boys and 3 girls ranging in age from 3 months to 29 months. RESULTS: A soft tissue mass was the chief complaint in 7 patients, abdominal distension in 1 patient with a retroperitoneal mass, and defecation difficulty in 1 patient with a perirectal mass. In 4 patients, tumors occurred on the back. Other tumor location includes the neck, scrotum, retroperitoneum, perirectal area, and buttock in 1 patient each. Lesions measured 2.3 to 19.5 cm. Complete excision was done in 8 patients. One perirectal tumor was removed by both the posterior sagittal approach and the intraabdominal approach but incompletely resected. Two tumors located on the back recurred with intraspinal extension 12 months and 18 months after resection. Second resection and second resection with laminectomy were done. Leg pain and urinary incontinence developed in 1 patient but improved on conservative treatment. CONCLUSIONS: Lipoblastoma is a benign neoplasm but can frequently recur (25%) in spite of complete excision. Lipoblastomas occurring on the back had a high recurrence rate (50%) and associated with intraspinal extension.
TREATMENT
SURGERY
Is surgical treatment of lipoblastoma always necessary? Mognato G, Cecchetto G, Carli M, Talenti E, d'Amore ES, Pederzini F, Guglielmi M. Department of Pediatrics, University of Padua, Italy.	J Pediatr Surg 2000 Oct;35(10):1511-3 Abstract quote Lipoblastoma is an uncommon, benign mesenchymal tumor with an excellent prognosis despite its potential to local invasion and rapid growth. However, in the literature, a spontaneous resolution has never been reported, and, consequently, the need for a complete surgical excision has never been questioned. The authors report a case of a 2-day-old boy with congenital diffuse lipoblastoma in the left thigh, which forced us to withhold from surgical treatment to avoid the risk of mutilation in a patient so young. The lesion was followed-up by imaging, and a complete spontaneous resolution of the diffuse lipoblastoma was shown by magnetic resonance imaging (MRI) at 1-year follow-up. In the literature, a complete surgical excision is recommended. The results of this case suggest that a "wait and see" approach is justified at least in infants with huge invasive lesions requiring a mutilating excision.
Lipoblastoma: pathophysiology and surgical management. Dilley AV, Patel DL, Hicks MJ, Brandt ML. Department of Surgery, Baylor College of Medicine, Houston, TX 77030, USA.	J Pediatr Surg 2001 Jan;36(1):229-31 Abstract quote BACKGROUND/PURPOSE: Lipoblastoma/lipoblastomatosis is a poorly understood and uncommon soft tissue tumor of infancy and early childhood. Twenty-four patients that presented to a single institution over a 15-year period were reviewed for clinical features and outcome. METHODS: A retrospective review was conducted. RESULTS: Twenty-five cases were identified; 1 chart was not available for review. Fourteen girls and 11 boys with a median age of 20 months (2 months, 10 years) presented with 26 separate tumors. Nineteen were focal and 7 diffuse. The tumors were located on the trunk (n = 13), leg (n = 6), arm (n = 3), and head and neck (n = 4). Five patients (all with diffuse type) had up to 3 recurrences. CONCLUSIONS: Patients with focal lipoblastoma are unlikely to require further surgery after initial resection. Patients with diffuse lipoblastoma (lipoblastomatosis) are likely to have recurrent disease (usually within 2 years) and should undergo close follow-up. Genetic analysis of the specimen will help exclude liposarcoma. Recurrent lesions are best imaged with magnetic resonance imaging to assess extent and plan reconstruction if necessary.

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
Internet Links

SPECIAL STAINS/ IMMUNOPEROXIDASE/ OTHER	CHARACTERIZATION
SPECIAL STAINS
IMMUNOPEROXIDASE
ELECTRON MICROSCOPY
Lipoblastoma and lipoblastomatosis in infancy and childhood: histopathologic, ultrastructural, and cytogenetic features. Hicks J, Dilley A, Patel D, Barrish J, Zhu SH, Brandt M. Department of Pathology, Texas Children's Hospital and Baylor College of Medicine, Houston 77030-2399, USA.	Ultrastruct Pathol 2001 Jul-Aug;25(4):321-33 Abstract quote Lipoblastoma is a relatively rare tumor that occurs in infancy and early childhood and arises from embryonic white fat. Although a benign tumor, lipoblastomas tend to recur and may resemble myxoid liposarcoma. The authors report 26 cases over a 15-year period at Texas Children's Hospital. There was a slight female predilection (14F:12M). The most common symptom was a painless mass with or without increasing size. The trunk, extremities, head and neck, retroperitoneum, inguinal canal, peritoneal cavity, and lung were the tumor sites. Most tumors were circumscribed lipoblastomas and the minority were diffuse infiltrative lipoblastomatosis. Reexcision for residual or recurrent tumor was necessary more frequently in patients with lipoblastomatosis. Histopathologic examination and ultrastructural examination revealed cellular neoplasms composed of immature adipocytes with relatively well-defined septa, frequent lipoblasts, a fine vascular network, and often a myxoid appearance resembling myxoid liposarcoma. Cytogenetics was performed in 4 cases with chromosome 8q abnormality being most common. The major concern with lipoblastoma in children is to completely excise the tumor to avoid leaving residual tumor and to prevent recurrences. Confusion with myxoid liposarcoma, well-differentiated liposarcoma, and typical lipomas may occur. Although asymptomatic, lipoblastomas may cause dysfunction of other organ systems due to mass effect. Complete surgical excision with at least 2 years of follow-up is the preferred therapy.

DIFFERENTIAL DIAGNOSIS	KEY DIFFERENTIATING FEATURES
LIPOMA
LIPOSARCOMA
Benign lipoblastoma and myxoid liposarcoma: a comparative light- and electron-microscopic study. Bolen JW, Thorning D.	Am J Surg Pathol 1980 Apr;4(2):163-74 Abstract quote A benign lipoblastoma and a myxoid liposarcoma were studied by light and electron microscopy. Both of these neoplasms had prominent plexiform vascular networks, early acquisition of fat by vascular pericytes, and progressive accumulation of fat by cells located away from the vasculature. Their component cells had investing basal laminae, pinocytotic vesicles, and cytoplasmic glycogen stores as well as cytoplasmic lipid. The process of neoplastic lipogenesis and the structural features of the neoplastic cells in both neoplasms resembled those of developing non-neoplastic fat tissue. The benign lipoblastoma appears to be analogous to developing fat, while the myxoid liposarcoma appears to recapitulate the actively proliferating zone of developing fat. The relationship between proliferating cells and the plexiform vascular network in all three processes is emphasized. We hypothesize that the vascular pericyte serves as a source for new fat storing cells.
Lipoblastoma and liposarcoma in children: an analysis of 9 cases and a review of the literature. Miller GG, Yanchar NL, Magee JF, Blair GK. Department of Surgery, University of British Columbia, British Columbia's Children's Hospital, Vancouver.	Can J Surg 1998 Dec;41(6):455-8 Abstract quote OBJECTIVES: To review the experience at a children's hospital of lipoblastoma and liposarcoma and to identify any factors that would differentiate one type of tumour from the other. DESIGN: A retrospective case series. SETTING: British Columbia's Children's Hospital a tertiary-care pediatric centre. PATIENTS: All patients with a pathological diagnosis of lipoblastoma and liposarcoma recorded over 12 years. MAIN OUTCOME MEASURES: The frequency of lipoblastoma and liposarcoma, identified from biopsy specimens of pediatric adipose tumours. The clinical, pathological and cytogenetic variables between lipoblastoma and liposarcoma. RESULTS: One hundred and forty-nine adipose tumours were recorded. Seven (4.7%) were lipoblastomas and 2 (1.3%) were liposarcomas. All tumours presented as asymptomatic, slow-growing, soft-tissue masses. The children with lipoblastoma tended to be younger, but 29% were over 3 years of age. The liposarcoma patients were aged 9 and 14 years. One liposarcoma was of myxoid type and the other was a round cell variant. Karyotypes were reported for 1 lipoblastoma and 1 liposarcoma. The myxoid liposarcoma karyotype was 46,XY,t(12;16)(q13;p11), and the lipoblastoma was reported as 46,XY,der(8)?t(8q;?),+mar. CONCLUSIONS: Lipoblastoma is an unusual childhood neoplasm and liposarcoma is very rare in children. Both tumours may present in a similar fashion, and differentiating them histologically can be difficult. Age cannot be relied upon to accurately predict their behaviour. The tumour karyotype is very helpful in differentiating these neoplasms.