Pseudoangiomatous Hyperplasia of the Breast

Background

This is a rare but benign tumor of the breast. Its importance lies in the diagnostic skills of the pathologist, distinguishing it from a malignancy. PSH stands for pseudoangiomatous stromal hyperplasia. It is a diangosis that only a pathologist can render by examining the breast tissue under the microscope.

OUTLINE

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

Internet Links

DISEASE ASSOCIATIONS CHARACTERIZATION

FIBROADENOMA

Pseudoangiomatous hyperplasia of mammary stroma: a case of pure type after removal of fibroadenoma.

Fukunaga M.

Department of Pathology, The Jikei University School of Medicine, Tokyo, Japan.
APMIS 2001 Feb;109(2):113-6 Abstract quote
A case of pure pseudoangiomatous hyperplasia of the mammary stroma after removal of a fibroadenoma is described. The lesion, which was found in the right breast of a 40-year-old woman, was a well-circumscribed non-encapsulated, rubbery, lobulated mass measuring 40x40x35 mm.

Histologically, it consisted predominantly of a proliferation of spindle cells with interanastomosing vascular-like arrangements in the interlobular or interductal stroma. Neither cytological atypia nor mitotic figures were observed. The stroma contained abundant collagen with focal hyalinization. Focally, epithelial elements showed mild ductal hyperplasia. There was no fibroadenoma. Immunohistochemically, the spindle cells were positive for vimentin, CD34, alpha-smooth muscle actin, muscle actin, CD34, calponin, and progesterone receptors.

Ultrastructurally, many spindle cells had thin elongated cytoplasmic processes, which enveloped pseudovascular spaces containing a few collagenous fibrils, indicating fibroblastic cells. This lesion should be distinguished from other mammary fibrous and vascular lesions with which it may be confused.

GYNECOMASTIA

Rapid growth of pseudoangiomatous hyperplasia of mammary stroma in axillary gynecomastia in an immunosuppressed patient.

Seidman JD, Borkowski A, Aisner SC, Sun CC.

Department of Pathology, University of Maryland Medical System, University of Maryland Hospital, Baltimore.
Arch Pathol Lab Med 1993 Jul;117(7):736-8 Abstract quote
Pseudoangiomatous hyperplasia of mammary stroma is a rare, benign mesenchymal proliferation that sometimes mimics angiosarcoma.

To our knowledge, it has not been reported in men. We report the first case of this unusual entity in a man. This case was most unusual in that it occurred in a clinical setting of immunosuppression, in axillary gynecomastia, and was growing rapidly.

Gynecomastia in type-1 neurofibromatosis with features of pseudoangiomatous stromal hyperplasia with giant cells. Report of two cases.

Damiani S, Eusebi V.

Department of Oncology, Marcello Malpighi of the University of Bologna, Italy.
Virchows Arch 2001 May;438(5):513-6 Abstract quote
We describe the histological finding in two cases of gynecomastia in patients with von Recklinghausen's disease. The histological and immunohistochemical features of the two cases were reviewed and compared with those of five cases of gynecomastia in men without clinical evidence of neurofibromatosis.

In both patients bearing von Recklinghausen's disease, the breast stroma showed features consistent with pseudoangiomatous stromal hyperplasia (PASH). It was characterised by anastomosing empty spaces lined by spindle and multinucleated giant cells which were positive with CD34 and anti-vimentin antisera and negative with anti-FVIII and CD31 antisera. In two of five of the control cases without neurofibromatosis, the mammary stroma showed focal areas with features of PASH, but no multinucleated giant cells were present in any case. PASH with giant cells should be recognised as a feature of gynecomastia in von Recklinghausen's disease.

The presence of multinucleated giant cells is very unusual and, although more cases have to be studied, these cells seem to be a feature of PASH occurring in patients with von Recklinghausen's disease.

HIV

Pseudoangiomatous hyperplasia of mammary stroma in an HIV patient.

de Saint Aubain Somerhausen N, Larsimont D, Cluydts N, Heymans O, Verhest A.

Department of Pathology, Institut Jules Bordet, Bruxelles, Belgium.
Gen Diagn Pathol 1997 Dec;143(4):251-4 Abstract quote
Pseudoangiomatous hyperplasia of the mammary stroma is a benign mesenchymal proliferative lesion. It is rarely observed as a tumor mass that has to be differentiated from angiosarcoma.

We give a review of the literature and report a case unusual in that it occurred in a clinical setting of HIV infection, was rapidly growing, and has been the largest described so far.

PATHOGENESIS CHARACTERIZATION

MYOFIBROBLASTS

Pseudoangiomatous stromal hyperplasia (PASH). A mammary stromal tumor with myofibroblastic differentiation.

Powell CM, Cranor ML, Rosen PP.

Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Am J Surg Pathol 1995 Mar;19(3):270-7 Abstract quote
Pseudoangiomatous stromal hyperplasia (PASH) is frequently a microscopic incidental finding in breast biopsies performed for benign or malignant disease. However, it may also produce a mass lesion.

We reviewed PASH seen first as a tumor in 40 women aged 14 to 67 years (mean, 37 years). All but one lesion were clinically palpable. The exceptional tumor was found by mammography. The mass, typically unilateral, was usually diagnosed clinically as a fibroadenoma. Most specimens contained a well-circumscribed tumor with a firm white-gray cut surface. In six cases, there was no discrete gross lesion in the surgical specimen. Microscopically, there was a spectrum of pathological stromal changes ranging from classical PASH with anastomosing slit-shaped spaces outlined by flat, bland spindle cells to more proliferative lesions composed of bundles of plump spindle cells that obscured the underlying pseudoangiomatous architecture in the most florid lesions.

The spindle cells were vimentin and CD34 positive and factor VIII negative. In more cellular fascicular lesions, the stromal cells acquired desmin and actin positivity.These immunohistochemical features were consistent with myofibroblastic histogenesis of PASH. Reactivity for progesterone receptor (PR) typically exceeded estrogen receptor (ER) in the nuclei of stromal and glandular cells. In most lesions, the nuclei of stromal spindle cells were ER negative. The majority of the patients were treated by excisional biopsy. One lesion, incompletely excised, spontaneously regressed. One patient had bilateral mastectomies. Follow-up was 0.6-11 years (mean, 4.5 years). Five patients had ipsilateral recurrences, and two had subsequent contralateral PASH. The morphological spectrum of cellular proliferation and staining qualities indicates that the myofibroblast plays a major role in the histogenesis of PASH.

The pathogenesis of PASH remains uncertain, but aberrant reactivity of myofibroblasts to endogenous or exogenous hormones is likely to be an important factor. Simple excision is adequate treatment initially and for infrequent recurrences, Diffuse PASH occasionally presents a difficult management problem that may necessitate mastectomy.

LABORATORY/
RADIOLOGIC/
OTHER TESTS
CHARACTERIZATION

RADIOLOGIC

Pseudoangiomatous stromal hyperplasia: mammographic, sonographic, and clinical patterns.

Cohen MA, Morris EA, Rosen PP, Dershaw DD, Liberman L, Abramson AF.

Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Radiology 1996 Jan;198(1):117-20 Abstract quote
PURPOSE: To analyze the mammographic, ultrasonographic (US), and clinical patterns of pseudoangiomatous stromal hyperplasia (PASH).

MATERIALS AND METHODS: Preoperative mammographic and US images, clinical records, and histologic assessments were reviewed in seven cases of PASH as the sole component or dominant stromal component of a clinically or mammographically defined mass lesion. In five, a PASH tumor was diagnosed at image-guided 14-gauge core-needle biopsy; in two, it was diagnosed at surgical excisional biopsy.

RESULTS: Four women were premenopausal, two were postmenopausal, and one 40-year-old patient had iatrogenic primary amenorrhea. Four of seven masses were palpable; three were discovered at mammography. Four masses enlarged over 6 months to 5 years. At mammography, all masses lacked calcifications; six were well defined, and one was spiculated. One was inapparent at US; the remaining six were well defined and hypoechoic.

CONCLUSION: The diagnosis of this rare lesion with image-guided breast biopsy or surgical biopsy is consistent with a well-defined uncalcified mass at mammography and a solid hypoechoic mass at US, usually in a premenopausal woman.

Pseudoangiomatous stromal hyperplasia: mammographic and sonographic appearances.

Polger MR, Denison CM, Lester S, Meyer JE.

Department of Radiology, Brigham and Women's Hospital, Boston, MA 02115, USA.
AJR Am J Roentgenol 1996 Feb;166(2):349-52 Abstract quote
OBJECTIVE: Pseudoangiomatous stromal hyperplasia is a benign, localized form of stromal overgrowth with a probable hormonal etiology. Our purpose is to describe the mammographic, sonographic, and clinical features of this entity.

MATERIALS AND METHODS: A retrospective review of breast imaging studies and demographic information for seven patients identified as having pseudoangiomatous stromal hyperplasia was performed. The patients were chosen from a 1-year period during which 1661 breast biopsies were performed.

RESULTS: The patients were 36-61 years old. Six were premenopausal, and the one postmenopausal woman was on hormone replacement therapy. Three patients wee evaluated palpable breast lumps, and four were asymptomatic. All seven women had noncalcified masses that measured 1.1-11 cm and that were visible by mammography. The border characteristics were as follows: three masses were well circumscribed, two were partly circumscribed, and two were indistinct, probably because they were obscured by overlying parenchyma. Sonography was performed for five patients; lesions were visible in four. All four of these lesions were solid and circumscribed. Five of the masses had increased in size since earlier studies, and one palpable mass was found by physical examination to have grown over time. Two patients had a local recurrence of pseudoangiomatous stromal hyperplasia. Surgical excision was performed for three patients, large-core biopsy was performed for three patients, and both surgery and large-core biopsy were performed for one patient.

ONCLUSION: Pseudoangiomatous stromal hyperplasia should be included in the differential diagnosis of a circumscribed or partially circumscribed mass, especially in the premenopausal population. These masses often grow over time and can recur locally. Pathologic diagnosis of the lesion may be difficult unless the pathologist is aware of the presence of a mass lesion and appreciates the stromal changes characteristic of such a lesion.

Imaging appearances of pseudoangiomatous hyperplasia of mammary stroma.

Kirkpatrick UJ, Burrows C, Loughran CF.

Department of Surgery, Macclesfield District General Hospital, Cheshire SK10 3BL, UK.
Clin Radiol 2000 Jul;55(7):576-8

LABORATORY MARKERS

GROSS APPEARANCE/
CLINICAL VARIANTS CHARACTERIZATION

GENERAL

Pseudoangiomatous stromal hyperplasia of the breast.

Castro CY, Whitman GJ, Sahin AA.

Department of Pathology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA.
Am J Clin Oncol 2002 Apr;25(2):213-6 Abstract quote
Pseudoangiomatous stromal hyperplasia is a benign proliferative lesion of the mammary stroma that rarely presents as a localized mass. We describe the clinical, radiologic, cytologic, and histologic features of a case of pseudoangiomatous stromal hyperplasia that presented as a rapidly growing breast lesion in a 36-year-old woman.

VARIANTS

ANOGENITAL

Pseudoangiomatous Stromal Hyperplasia in Lesions Involving Anogenital Mammary-Like Glands.

Kazakov DV, Bisceglia M, Mukensnabl P, Michal M.

From *Sikl's Department of Pathology, Charles University, Medical Faculty Hospital, Pilsen, Czech Republic; and daggerDepartment of Pathology, IRCCS-Ospedale "Casa Sollievo della Sofferenza," San Giovanni Rotondo, Italy.

Am J Surg Pathol. 2005 Sep;29(9):1243-1246. Abstract quote

Pseudoangiomatous stromal hyperplasia (PASH), first reported in 1986, is nowadays a well-recognized change in the breast.

We present three cases of lesions involving anogenital mammary-like glands demonstrating this feature. All patients were females (ages, 42, 43, and 53 years). Each presented with a solitary, 1.5- to 2-cm asymptomatic nodule. Locations included the perianal area, perineum, and labium majus.

Histopathologically, one lesion was classified as low-grade phyllodes tumor, another as fibroadenoma, and in the remaining case PASH was found in the background of mild hyperplasia of anogenital mammary-like glands and substantial lipomatous metaplasia. In all lesions, PASH had an identical appearance to that in the breast, that is open, slit-like, often anastomosing channels devoid of erythrocytes and lined by discontinuous, often attenuated, inconspicuous cells without atypia or mitotic activity set in a hyalinized collagenous stroma. Quantitatively, PASH ranged in the above cases, forming a relatively small focus in the fibroadenoma and being quite extensive in the remaining two cases. In the phyllodes tumor, PASH areas exhibited focal hypercellularity and presence of myoid cells. In none of the cases were there cells with intranuclear inclusions or multinucleated cells. The lesions were surgically excised. Two patients with follow-up were disease-free at one and three years after the operation.

As to our knowledge, PASH has not been previously described in the anogenital area, this feature seems to have been either overlooked or is genuinely rare in this location. It may occur in a preexisting lesion of anogenital mammary-like glands or may apparently by itself produce a clinically detectable lesion. The clinicopathologic features of PASH in the anogenital area seem to be identical to those in the breast.

MALE BREAST

Pseudoangiomatous hyperplasia of male breast.

Badve S, Sloane JP.

Department of Histopathology, Royal Marsden Hospital, Sutton, Surrey, UK.
Histopathology 1995 May;26(5):463-6 Abstract quote
Ninety-three male breast specimens have been examined for the presence of pseudoangiomatous hyperplasia of the mammary stroma which has hitherto been described almost exclusively in females.

Forty-four cases (47.4%) showed some degree of hyperplasia, varying from small microscopic foci to extensive change involving 90% of the mammary tissue. All but one were found in association with gynaecomastia, early and intermediate stage.

The association between pseudoangiomatous hyperplasia and benign proliferative lesions mirrors that reported in the female breast, and our findings suggest that the change may represent a stage in the maturation of newly formed mammary stroma.

MASS

Pseudoangiomatous stromal hyperplasia: presentation as a mass in the female nipple.

Iancu D, Nochomovitz LE.

Department of Pathology, Winthrop-University Hospital, Mineola, New York 11501, USA.
Breast J 2001 Jul-Aug;7(4):263-5 Abstract quote
Pseudoangiomatous stromal hyperplasia (PASH) is a benign, localized fibroblastic and myofibroblastic overgrowth that occurs almost exclusively in premenopausal women as a painless, palpable intramammary mass.

The lesion has a pale, fibrous, and homogeneous cut surface, is typically well circumscribed, and may have a diameter of 2.0-15 cm. Its ramifying slits lined by flattened myofibroblastic cells are apt to be mistaken for vascular spaces, leading to an erroneous diagnosis of angiosarcoma. The etiology of the condition is unknown, but a relationship to myofibroblastoma has been postulated. Hormonal factors, too, are thought to play a developmental role.

The potential for PASH to create a palpable breast mass has been only quite recently advanced in the medical literature, and it has evidently not been reported in the nipple.

HISTOLOGICAL TYPES CHARACTERIZATION

GENERAL

Pseudoangiomatous hyperplasia of mammary stroma. Some observations regarding its clinicopathologic spectrum.

Ibrahim RE, Sciotto CG, Weidner N.

Department of Pathology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02115.
Cancer 1989 Mar 15;63(6):1154-60 Abstract quote
Pseudoangiomatous hyperplasia of mammary stroma (PHMS) is a benign proliferation of keloid-like fibrosis, containing slit-like pseudovascular spaces. Its main importance is its distinction from angiosarcoma; however, the clinicopathologic spectrum of PHMS remains incompletely described.

We report two new cases and describe our findings in 200 consecutive breast specimens evaluated for the presence of PHMS. The first patient presented with peau-de-orange change in the overlying breast skin, thus mimicking inflammatory breast carcinoma. Furthermore, this patient's PHMS lesion had been diagnosed and treated inappropriately as a low-grade angiosarcoma. The second case showed the more typical, fibroadenoma-like presentation of PHMS. In addition, PHMS changes occur commonly in routine breast biopsy specimens. In fact, our review of 200 consecutive breast specimens showed PHMS in at least one microscopic focus in 23% of cases. The PHMS changes occurred in younger patients than the control population and were associated with fibrocystic changes, in fibroadenomas, in gynecomastia, in normal breast tissue, and in sclerosing lobular hyperplasia.

Ultrastructural and immunohistochemical studies of one case showed that the capillary-like spaces were either acellular or lined by fibroblasts. Pseudoangiomatous hyperplasia of mammary stroma represents a clinicopathologic spectrum, extending from focal, insignificant microscopic changes to cases where PHMS produces a breast mass. Increased awareness of PHMS and its clinicopathologic spectrum will allow its differentiation from other vascular tumors of the breast, especially low-grade angiosarcoma.

CYTOLOGY

Nodular pseudoangiomatous stromal hyperplasia of the breast. Cytologic features.

Vicandi B, Jimenez-Heffernan JA, Lopez-Ferrer P, Ortega L, Viguer JM.

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

Acta Cytol 1998 Mar-Apr;42(2):335-41 Abstract quote
OBJECTIVE: To define and discuss the cytologic findings in six cases of nodular pseudoangiomatous stromal hyperplasia (PASH) of the breast.

STUDY DESIGN: Retrospective evaluation of the medical records, cytologic and histologic material from six patients with palpable mammary PASH. Cases in which PASH was associated with other predominant mammary lesions were not included in the study.

RESULTS: A total of six patients with histologically proven PASH underwent aspiration in nine occasions (three patients studied twice). Clinically, five patients were diagnosed as having fibroadenoma or another benign lesion, and in one patient carcinoma was suspected. In two patients, mammography disclosed rapid growth of the lesion. Seven aspirations, performed on five patients, were diagnosed as fibroadenoma (n = 5) or fibroadenomatous lesion (n = 2). An eighth aspiration was cystic and reported as fibrocystic disease. The last case was erroneously diagnosed as suspicious for carcinoma. Even after revision, the cytologic similarities of PASH with fibroadenoma were remarkable. Most smears were less cellular than those of conventional fibroadenomas. Epithelial clusters showed variable size, with a predominance of medium to small groups. Stromal elements were minimal or absent. Background cellularity was composed of round to oval naked nuclei and others with spindle shapes. Occasional epithelial clusters showed cellular dissociation and slight atypia.

CONCLUSION: Due to the absence of specific cytologic features and similarities to fibroadenoma, a precise diagnosis of PASH cannot be made on cytologic material. However, the majority of cases can be diagnosed correctly as benign, allowing appropiate treatment.

Fine needle aspiration cytology of mammary pseudoangiomatous stromal hyperplasia. A case report.

McCluggage WG, Allen M, Anderson NH.

Department of Cytopathology and Histopathology, Royal Group of Hospitals Trust, Belfast, Northern Ireland.
Acta Cytol 1999 Nov-Dec;43(6):1147-9 Abstract quote
BACKGROUND: Pseudoangiomatous stromal hyperplasia (PASH) is an unusual benign breast lesion that may occasionally present as a palpable mass. CASE: This report describes the fine needle aspiration cytology (FNAC) features of a case of mammary PASH that presented as a palpable mass. This is the second description of the FNAC features of this lesion and the first reported case in which a diagnosis of phyllodes tumor was considered. The aspirate was cellular and contained cohesive groups of cells in which there was a dual population of epithelial and myoepithelial cells. Occasional cellular stromal fragments were present, as were typical, bipolar, bare nuclei. Admixed with the bare nuclei were large numbers of plump, spindle-shaped cells, some with intact cytoplasm. Histologic examination of the excised mass showed features typical of PASH.

CONCLUSION: Mammary PASH may present as a palpable mass and is likely to be encountered in FNAC specimens. This diagnosis should be considered when one is confronted with an aspirate containing cohesive epithelial groups, cellular stromal fragments and large numbers of single, spindle-shaped cells. These features on FNAC may result in consideration of a phyllodes tumor. The single, spindle-shaped cells may be a characteristic cytologic feature of PASH.

SPECIAL STAINS/
IMMUNOPEROXIDASE/
OTHER CHARACTERIZATION

SPECIAL STAINS

IMMUNOPEROXIDASE

GENERAL

Expression of CD34 and bcl-2 in phyllodes tumours, fibroadenomas and spindle cell lesions of the breast.

Moore T, Lee AH.

University Department of Pathology, Southampton General Hospital, Southampton, UK.
Histopathology 2001 Jan;38(1):62-7 Abstract quote
AIMS: Strong expression of CD34 and bcl-2 has been described in solitary fibrous tumours. It has been proposed that these lesions arise from long-lived mesenchymal cells. We tested the hypothesis that spindle cell lesions of the breast arise from similar mesenchymal cells in the mammary stroma.

METHODS and RESULTS: Sections of phyllodes tumours (26), fibroadenomas (15), myofibroblastomas (two), pseudoangiomatous hyperplasia (five) and myoid hamartoma (one) were stained immunohistochemically for CD34 and bcl-2. Conventional mammary carcinoma is known to be CD34-negative: we therefore stained 11 spindle cell carcinomas and one adenosquamous carcinoma. The mammary stroma, particularly around lobules, stained for CD34. All the lesions (except the carcinomas) showed spindle cell staining for CD34. There was more staining in fibroadenomas than in phyllodes tumours (especially malignant tumours). The staining in phyllodes tumours was typically patchy. In some there was increased or decreased staining adjacent to the epithelium. There were occasional spindle cells positive for bcl-2 in the normal perilobular stroma. bcl-2 was frequently expressed in spindle cells in fibroadenomas, phyllodes tumours and pseudoangiomatous hyperplasia, and rarely in the other lesions.

CONCLUSIONS: The combined expression of CD34 and bcl-2 suggests that fibroadenomas, phyllodes tumours and pseudoangiomatous hyperplasia may arise from long-lived bcl-2-positive mesenchymal cells in the breast in a manner similar to that proposed for solitary fibrous tumours. The absence of CD34 staining in spindle cell carcinomas is of potential diagnostic value in the distinction from malignant phyllodes tumours in difficult cases.

HORMONAL RECEPTORS

Immunocytochemical analysis of estrogen and progesterone receptors in benign stromal lesions of the breast. Evidence for hormonal etiology in pseudoangiomatous hyperplasia of mammary stroma.

Anderson C, Ricci A Jr, Pedersen CA, Cartun RW.

Department of Pathology and Laboratory Medicine, Hartford Hospital, Connecticut 06115-0729.
Am J Surg Pathol 1991 Feb;15(2):145-9 Abstract quote
Five cases of pseudoangiomatous hyperplasia of mammary stroma, together with seven examples of mammary hamartoma, were probed with monoclonal antibodies H222 and KD68 to investigate the possible role of estrogen and progesterone receptor expression in the pathogenesis of these benign stromal proliferations.

All five cases of pseudoangiomatous hyperplasia showed patchy, intense labelling of the stromal cells with progesterone receptor antibodies, a pattern contrasting markedly with the absence of immunoreactivity in normal (nongestational) mammary stroma or the stromal component of common juvenile mammary hyperplasia. The stroma of the hamartoma group labeled inconsistently, with the notable exception of three myoid hamartomas. Stromal immunoreactivity was diffuse and intense in two of these, and patchy and distinct in the remaining case.

These findings (a) support the contention that pseudoangiomatous hyperplasia represents a localized form of stromal overgrowth with a hormonal (primarily progestagenic) etiology and (b) further highlight the heterogeneity of so-called mammary hamartomas by demonstrating dramatically different progesterone receptor immunoreactivity patterns in myoid lesions as compared with other hamartoma variants.

DIFFERENTIAL DIAGNOSIS KEY DIFFERENTIATING FEATURES

ANGIOSARCOMA

MAMMARY HAMARTOMA

Mammary hamartomas--a report of 15 cases.

Rege JD, Shet TM, Pathak VM, Zurale DU.

Department of Pathology, Topiwala National Medical College, Bombay Central, Bombay.
Indian J Pathol Microbiol 1997 Oct;40(4):543-8 Abstract quote
The mammary hamartoma is a poorly recognised benign breast neoplasm. For diagnosis one usually correlates the clinical, mammographic, gross and histologic features.

This study of fifteen cases emphasises the histomorphologic criteria for diagnosis especially in the absence of mammographic picture, viz. a clinically palpable, well encapsulated mass which on histology shows normal breast epithelium admixed with fat, fibrous tissue and other mesenchymal elements. The epithelium in the hamartomas studied showed changes seen in normal breast especially in the progestational phase of the menstrual cycle.

The stroma was either densely collagenous, hyalinised or cellular and admixed with fat in various proportion in thirteen cases, muscle in two cases and thick muscular arteries in four cases. It also showed pseudoangiomatous hyperplasia in seven cases. The importance of this change and probable evolution is discussed therein.

MAMMARY MYOFIBROBLASTOMA

Uncommon presentation of mammary myofibroblastoma.

Hamele-Bena D, Cranor ML, Sciotto C, Erlandson R, Rosen PP.

Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York 10021, USA.
Mod Pathol 1996 Jul;9(7):786-90 Abstract quote
Myofibroblastoma, a rare benign mesenchymal mammary neoplasm, has been diagnosed largely in men as a unilateral, solitary lesion.

We studied nine examples occurring in the breasts of eight patients, all but one of whom were women. In the man, the lesions were bilateral. Patients ranged in age from 44 to 67 years (mean and median, 55 yr). The tumors were well circumscribed and measured 0.9 to 3.0 cm (mean, 1.5 cm). They were composed of cells with a spectrum of appearances including small, compact cells, spindle cells, large histiocytoid cells, and epithelioid cells. All had broad bands of dense collagen, and adipose tissue was present in seven tumors. Foci of pseudoangiomatous hyperplasia were present in two cases. Strong vimentin positivity was present in seven tumors, which were cytokeratin negative. Weak S100 positivity was demonstrated in one lesion, and actin was positive in two lesions. Desmin was positive in six tumors and negative in one tumor. Treatment for all of the patients was excisional biopsy. Follow-up, available in five cases, was from 10 months to 6 years, 11 months (mean, 37 mo; median, 63 mo). All patients are alive and without evidence of disease.

The clinical and pathologic characteristics of myofibroblastoma in women are similar to published data on the tumor in men. The tumors exhibit heterogeneous immunoreactivity for markers associated with myofibroblasts. Excisional biopsy is adequate therapy.

PROGNOSIS AND TREATMENT CHARACTERIZATION

PROGNOSTIC FACTORS

Pseudoangiomatous hyperplasia of mammary stroma.

Vuitch MF, Rosen PP, Erlandson RA.
Hum Pathol 1986 Feb;17(2):185-91 Abstract quote
Grossly circumscribed, nonhemorrhagic breast masses consisting of mammary stromal proliferations that simulated vascular lesions were studied in nine women. Histologically, a striking pattern, which appeared to consist of complex inter-anastomosing channels lined by slender spindle cells, was present in the mammary parenchyma. The importance of this benign lesion, referred to as pseudoangiomatous hyperplasia of mammary stroma, is its distinction from angiosarcoma.

The patients ranged in age from 22 to 52 years; all were premenopausal. Each presented with a palpable unilateral mass, measuring up to 7 cm in diameter. The patients were treated by excisional biopsy and remained well for up to 2.5 years after excision. One patient had two local recurrences within one year of the original excision, and a second patient had a local recurrence at 14 months. No patient had another concurrent or metachronous malignant tumor of the breast or other organ, and no abnormal hormonal status was found. Complete local excision appears to be adequate treatment. It remains to be determined whether this is a neoplastic process.

However, there is no evidence that it is a precursor of angiosarcoma, and ultrastructural observations demonstrate that the spaces found in the lesion are not true vascular channels. Rather, they appear to arise by a process that involves disruption and separation of stromal collagen fibers. Since small foci of this change are common in hyperplastic breast tissue from premenopausal women, it is likely that the development of a discrete tumor with this pattern represents an exaggerated form of stromal hyperplasia.

TREATMENT

TAMOXIFEN

Tamoxifen in the management of pseudoangiomatous stromal hyperplasia.

Pruthi S, Reynolds C, Johnson RE, Gisvold JJ.

Division of General Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.
Breast J 2001 Nov-Dec;7(6):434-9 Related Articles, Books, LinkOut

Tamoxifen in the management of pseudoangiomatous stromal hyperplasia.

Pruthi S, Reynolds C, Johnson RE, Gisvold JJ.

Division of General Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.

Pseudoangiomatous stromal hyperplasia (PASH) is a relatively uncommon histologic finding in breast specimens. The clinicopathologic spectrum of this disease entity can range from a focal nonsignificant microscopic finding to a dominant palpable breast mass. To confirm the diagnosis, a biopsy is required primarily to distinguish PASH from a low-grade angiosarcoma. The mammographic description of PASH is a round or ovoid, circumscribed or partially circumscribed mass. The sonographic feature is a hypoechoic mass. PASH is similar to a fibroadenoma in clinical and imaging features. Progressive breast enlargement associated with engorgement, cyclical breast pain, and burning sensation is of significant concern for some women. The management of the palpable mass and associated symptoms has included excisional biopsy, often leading to recurrent excisions and even mastectomy. This report documents an impressive response to tamoxifen in a patient with PASH presenting with breast enlargement, pain, and breast masses. To our knowledge, there are no reports on the use of tamoxifen or other selective estrogen receptor modulators in the management of this benign breast condition.

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DISEASE ASSOCIATIONS	CHARACTERIZATION
FIBROADENOMA
Pseudoangiomatous hyperplasia of mammary stroma: a case of pure type after removal of fibroadenoma. Fukunaga M. Department of Pathology, The Jikei University School of Medicine, Tokyo, Japan.	APMIS 2001 Feb;109(2):113-6 Abstract quote A case of pure pseudoangiomatous hyperplasia of the mammary stroma after removal of a fibroadenoma is described. The lesion, which was found in the right breast of a 40-year-old woman, was a well-circumscribed non-encapsulated, rubbery, lobulated mass measuring 40x40x35 mm. Histologically, it consisted predominantly of a proliferation of spindle cells with interanastomosing vascular-like arrangements in the interlobular or interductal stroma. Neither cytological atypia nor mitotic figures were observed. The stroma contained abundant collagen with focal hyalinization. Focally, epithelial elements showed mild ductal hyperplasia. There was no fibroadenoma. Immunohistochemically, the spindle cells were positive for vimentin, CD34, alpha-smooth muscle actin, muscle actin, CD34, calponin, and progesterone receptors. Ultrastructurally, many spindle cells had thin elongated cytoplasmic processes, which enveloped pseudovascular spaces containing a few collagenous fibrils, indicating fibroblastic cells. This lesion should be distinguished from other mammary fibrous and vascular lesions with which it may be confused.
GYNECOMASTIA
Rapid growth of pseudoangiomatous hyperplasia of mammary stroma in axillary gynecomastia in an immunosuppressed patient. Seidman JD, Borkowski A, Aisner SC, Sun CC. Department of Pathology, University of Maryland Medical System, University of Maryland Hospital, Baltimore.	Arch Pathol Lab Med 1993 Jul;117(7):736-8 Abstract quote Pseudoangiomatous hyperplasia of mammary stroma is a rare, benign mesenchymal proliferation that sometimes mimics angiosarcoma. To our knowledge, it has not been reported in men. We report the first case of this unusual entity in a man. This case was most unusual in that it occurred in a clinical setting of immunosuppression, in axillary gynecomastia, and was growing rapidly.
Gynecomastia in type-1 neurofibromatosis with features of pseudoangiomatous stromal hyperplasia with giant cells. Report of two cases. Damiani S, Eusebi V. Department of Oncology, Marcello Malpighi of the University of Bologna, Italy.	Virchows Arch 2001 May;438(5):513-6 Abstract quote We describe the histological finding in two cases of gynecomastia in patients with von Recklinghausen's disease. The histological and immunohistochemical features of the two cases were reviewed and compared with those of five cases of gynecomastia in men without clinical evidence of neurofibromatosis. In both patients bearing von Recklinghausen's disease, the breast stroma showed features consistent with pseudoangiomatous stromal hyperplasia (PASH). It was characterised by anastomosing empty spaces lined by spindle and multinucleated giant cells which were positive with CD34 and anti-vimentin antisera and negative with anti-FVIII and CD31 antisera. In two of five of the control cases without neurofibromatosis, the mammary stroma showed focal areas with features of PASH, but no multinucleated giant cells were present in any case. PASH with giant cells should be recognised as a feature of gynecomastia in von Recklinghausen's disease. The presence of multinucleated giant cells is very unusual and, although more cases have to be studied, these cells seem to be a feature of PASH occurring in patients with von Recklinghausen's disease.
HIV
Pseudoangiomatous hyperplasia of mammary stroma in an HIV patient. de Saint Aubain Somerhausen N, Larsimont D, Cluydts N, Heymans O, Verhest A. Department of Pathology, Institut Jules Bordet, Bruxelles, Belgium.	Gen Diagn Pathol 1997 Dec;143(4):251-4 Abstract quote Pseudoangiomatous hyperplasia of the mammary stroma is a benign mesenchymal proliferative lesion. It is rarely observed as a tumor mass that has to be differentiated from angiosarcoma. We give a review of the literature and report a case unusual in that it occurred in a clinical setting of HIV infection, was rapidly growing, and has been the largest described so far.

LABORATORY/ RADIOLOGIC/ OTHER TESTS	CHARACTERIZATION
RADIOLOGIC
Pseudoangiomatous stromal hyperplasia: mammographic, sonographic, and clinical patterns. Cohen MA, Morris EA, Rosen PP, Dershaw DD, Liberman L, Abramson AF. Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.	Radiology 1996 Jan;198(1):117-20 Abstract quote PURPOSE: To analyze the mammographic, ultrasonographic (US), and clinical patterns of pseudoangiomatous stromal hyperplasia (PASH). MATERIALS AND METHODS: Preoperative mammographic and US images, clinical records, and histologic assessments were reviewed in seven cases of PASH as the sole component or dominant stromal component of a clinically or mammographically defined mass lesion. In five, a PASH tumor was diagnosed at image-guided 14-gauge core-needle biopsy; in two, it was diagnosed at surgical excisional biopsy. RESULTS: Four women were premenopausal, two were postmenopausal, and one 40-year-old patient had iatrogenic primary amenorrhea. Four of seven masses were palpable; three were discovered at mammography. Four masses enlarged over 6 months to 5 years. At mammography, all masses lacked calcifications; six were well defined, and one was spiculated. One was inapparent at US; the remaining six were well defined and hypoechoic. CONCLUSION: The diagnosis of this rare lesion with image-guided breast biopsy or surgical biopsy is consistent with a well-defined uncalcified mass at mammography and a solid hypoechoic mass at US, usually in a premenopausal woman.
Pseudoangiomatous stromal hyperplasia: mammographic and sonographic appearances. Polger MR, Denison CM, Lester S, Meyer JE. Department of Radiology, Brigham and Women's Hospital, Boston, MA 02115, USA.	AJR Am J Roentgenol 1996 Feb;166(2):349-52 Abstract quote OBJECTIVE: Pseudoangiomatous stromal hyperplasia is a benign, localized form of stromal overgrowth with a probable hormonal etiology. Our purpose is to describe the mammographic, sonographic, and clinical features of this entity. MATERIALS AND METHODS: A retrospective review of breast imaging studies and demographic information for seven patients identified as having pseudoangiomatous stromal hyperplasia was performed. The patients were chosen from a 1-year period during which 1661 breast biopsies were performed. RESULTS: The patients were 36-61 years old. Six were premenopausal, and the one postmenopausal woman was on hormone replacement therapy. Three patients wee evaluated palpable breast lumps, and four were asymptomatic. All seven women had noncalcified masses that measured 1.1-11 cm and that were visible by mammography. The border characteristics were as follows: three masses were well circumscribed, two were partly circumscribed, and two were indistinct, probably because they were obscured by overlying parenchyma. Sonography was performed for five patients; lesions were visible in four. All four of these lesions were solid and circumscribed. Five of the masses had increased in size since earlier studies, and one palpable mass was found by physical examination to have grown over time. Two patients had a local recurrence of pseudoangiomatous stromal hyperplasia. Surgical excision was performed for three patients, large-core biopsy was performed for three patients, and both surgery and large-core biopsy were performed for one patient. ONCLUSION: Pseudoangiomatous stromal hyperplasia should be included in the differential diagnosis of a circumscribed or partially circumscribed mass, especially in the premenopausal population. These masses often grow over time and can recur locally. Pathologic diagnosis of the lesion may be difficult unless the pathologist is aware of the presence of a mass lesion and appreciates the stromal changes characteristic of such a lesion.
Imaging appearances of pseudoangiomatous hyperplasia of mammary stroma. Kirkpatrick UJ, Burrows C, Loughran CF. Department of Surgery, Macclesfield District General Hospital, Cheshire SK10 3BL, UK.	Clin Radiol 2000 Jul;55(7):576-8
LABORATORY MARKERS

HISTOLOGICAL TYPES	CHARACTERIZATION
GENERAL
Pseudoangiomatous hyperplasia of mammary stroma. Some observations regarding its clinicopathologic spectrum. Ibrahim RE, Sciotto CG, Weidner N. Department of Pathology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02115.	Cancer 1989 Mar 15;63(6):1154-60 Abstract quote Pseudoangiomatous hyperplasia of mammary stroma (PHMS) is a benign proliferation of keloid-like fibrosis, containing slit-like pseudovascular spaces. Its main importance is its distinction from angiosarcoma; however, the clinicopathologic spectrum of PHMS remains incompletely described. We report two new cases and describe our findings in 200 consecutive breast specimens evaluated for the presence of PHMS. The first patient presented with peau-de-orange change in the overlying breast skin, thus mimicking inflammatory breast carcinoma. Furthermore, this patient's PHMS lesion had been diagnosed and treated inappropriately as a low-grade angiosarcoma. The second case showed the more typical, fibroadenoma-like presentation of PHMS. In addition, PHMS changes occur commonly in routine breast biopsy specimens. In fact, our review of 200 consecutive breast specimens showed PHMS in at least one microscopic focus in 23% of cases. The PHMS changes occurred in younger patients than the control population and were associated with fibrocystic changes, in fibroadenomas, in gynecomastia, in normal breast tissue, and in sclerosing lobular hyperplasia. Ultrastructural and immunohistochemical studies of one case showed that the capillary-like spaces were either acellular or lined by fibroblasts. Pseudoangiomatous hyperplasia of mammary stroma represents a clinicopathologic spectrum, extending from focal, insignificant microscopic changes to cases where PHMS produces a breast mass. Increased awareness of PHMS and its clinicopathologic spectrum will allow its differentiation from other vascular tumors of the breast, especially low-grade angiosarcoma.
CYTOLOGY
Nodular pseudoangiomatous stromal hyperplasia of the breast. Cytologic features. Vicandi B, Jimenez-Heffernan JA, Lopez-Ferrer P, Ortega L, Viguer JM. Department of Pathology, La Paz Hospital, Madrid, Spain.	Acta Cytol 1998 Mar-Apr;42(2):335-41 Abstract quote OBJECTIVE: To define and discuss the cytologic findings in six cases of nodular pseudoangiomatous stromal hyperplasia (PASH) of the breast. STUDY DESIGN: Retrospective evaluation of the medical records, cytologic and histologic material from six patients with palpable mammary PASH. Cases in which PASH was associated with other predominant mammary lesions were not included in the study. RESULTS: A total of six patients with histologically proven PASH underwent aspiration in nine occasions (three patients studied twice). Clinically, five patients were diagnosed as having fibroadenoma or another benign lesion, and in one patient carcinoma was suspected. In two patients, mammography disclosed rapid growth of the lesion. Seven aspirations, performed on five patients, were diagnosed as fibroadenoma (n = 5) or fibroadenomatous lesion (n = 2). An eighth aspiration was cystic and reported as fibrocystic disease. The last case was erroneously diagnosed as suspicious for carcinoma. Even after revision, the cytologic similarities of PASH with fibroadenoma were remarkable. Most smears were less cellular than those of conventional fibroadenomas. Epithelial clusters showed variable size, with a predominance of medium to small groups. Stromal elements were minimal or absent. Background cellularity was composed of round to oval naked nuclei and others with spindle shapes. Occasional epithelial clusters showed cellular dissociation and slight atypia. CONCLUSION: Due to the absence of specific cytologic features and similarities to fibroadenoma, a precise diagnosis of PASH cannot be made on cytologic material. However, the majority of cases can be diagnosed correctly as benign, allowing appropiate treatment.
Fine needle aspiration cytology of mammary pseudoangiomatous stromal hyperplasia. A case report. McCluggage WG, Allen M, Anderson NH. Department of Cytopathology and Histopathology, Royal Group of Hospitals Trust, Belfast, Northern Ireland.	Acta Cytol 1999 Nov-Dec;43(6):1147-9 Abstract quote BACKGROUND: Pseudoangiomatous stromal hyperplasia (PASH) is an unusual benign breast lesion that may occasionally present as a palpable mass. CASE: This report describes the fine needle aspiration cytology (FNAC) features of a case of mammary PASH that presented as a palpable mass. This is the second description of the FNAC features of this lesion and the first reported case in which a diagnosis of phyllodes tumor was considered. The aspirate was cellular and contained cohesive groups of cells in which there was a dual population of epithelial and myoepithelial cells. Occasional cellular stromal fragments were present, as were typical, bipolar, bare nuclei. Admixed with the bare nuclei were large numbers of plump, spindle-shaped cells, some with intact cytoplasm. Histologic examination of the excised mass showed features typical of PASH. CONCLUSION: Mammary PASH may present as a palpable mass and is likely to be encountered in FNAC specimens. This diagnosis should be considered when one is confronted with an aspirate containing cohesive epithelial groups, cellular stromal fragments and large numbers of single, spindle-shaped cells. These features on FNAC may result in consideration of a phyllodes tumor. The single, spindle-shaped cells may be a characteristic cytologic feature of PASH.

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
Internet Links

SPECIAL STAINS/ IMMUNOPEROXIDASE/ OTHER	CHARACTERIZATION
SPECIAL STAINS
IMMUNOPEROXIDASE
GENERAL
Expression of CD34 and bcl-2 in phyllodes tumours, fibroadenomas and spindle cell lesions of the breast. Moore T, Lee AH. University Department of Pathology, Southampton General Hospital, Southampton, UK.	Histopathology 2001 Jan;38(1):62-7 Abstract quote AIMS: Strong expression of CD34 and bcl-2 has been described in solitary fibrous tumours. It has been proposed that these lesions arise from long-lived mesenchymal cells. We tested the hypothesis that spindle cell lesions of the breast arise from similar mesenchymal cells in the mammary stroma. METHODS and RESULTS: Sections of phyllodes tumours (26), fibroadenomas (15), myofibroblastomas (two), pseudoangiomatous hyperplasia (five) and myoid hamartoma (one) were stained immunohistochemically for CD34 and bcl-2. Conventional mammary carcinoma is known to be CD34-negative: we therefore stained 11 spindle cell carcinomas and one adenosquamous carcinoma. The mammary stroma, particularly around lobules, stained for CD34. All the lesions (except the carcinomas) showed spindle cell staining for CD34. There was more staining in fibroadenomas than in phyllodes tumours (especially malignant tumours). The staining in phyllodes tumours was typically patchy. In some there was increased or decreased staining adjacent to the epithelium. There were occasional spindle cells positive for bcl-2 in the normal perilobular stroma. bcl-2 was frequently expressed in spindle cells in fibroadenomas, phyllodes tumours and pseudoangiomatous hyperplasia, and rarely in the other lesions. CONCLUSIONS: The combined expression of CD34 and bcl-2 suggests that fibroadenomas, phyllodes tumours and pseudoangiomatous hyperplasia may arise from long-lived bcl-2-positive mesenchymal cells in the breast in a manner similar to that proposed for solitary fibrous tumours. The absence of CD34 staining in spindle cell carcinomas is of potential diagnostic value in the distinction from malignant phyllodes tumours in difficult cases.
HORMONAL RECEPTORS
Immunocytochemical analysis of estrogen and progesterone receptors in benign stromal lesions of the breast. Evidence for hormonal etiology in pseudoangiomatous hyperplasia of mammary stroma. Anderson C, Ricci A Jr, Pedersen CA, Cartun RW. Department of Pathology and Laboratory Medicine, Hartford Hospital, Connecticut 06115-0729.	Am J Surg Pathol 1991 Feb;15(2):145-9 Abstract quote Five cases of pseudoangiomatous hyperplasia of mammary stroma, together with seven examples of mammary hamartoma, were probed with monoclonal antibodies H222 and KD68 to investigate the possible role of estrogen and progesterone receptor expression in the pathogenesis of these benign stromal proliferations. All five cases of pseudoangiomatous hyperplasia showed patchy, intense labelling of the stromal cells with progesterone receptor antibodies, a pattern contrasting markedly with the absence of immunoreactivity in normal (nongestational) mammary stroma or the stromal component of common juvenile mammary hyperplasia. The stroma of the hamartoma group labeled inconsistently, with the notable exception of three myoid hamartomas. Stromal immunoreactivity was diffuse and intense in two of these, and patchy and distinct in the remaining case. These findings (a) support the contention that pseudoangiomatous hyperplasia represents a localized form of stromal overgrowth with a hormonal (primarily progestagenic) etiology and (b) further highlight the heterogeneity of so-called mammary hamartomas by demonstrating dramatically different progesterone receptor immunoreactivity patterns in myoid lesions as compared with other hamartoma variants.

DIFFERENTIAL DIAGNOSIS	KEY DIFFERENTIATING FEATURES
ANGIOSARCOMA
MAMMARY HAMARTOMA
Mammary hamartomas--a report of 15 cases. Rege JD, Shet TM, Pathak VM, Zurale DU. Department of Pathology, Topiwala National Medical College, Bombay Central, Bombay.	Indian J Pathol Microbiol 1997 Oct;40(4):543-8 Abstract quote The mammary hamartoma is a poorly recognised benign breast neoplasm. For diagnosis one usually correlates the clinical, mammographic, gross and histologic features. This study of fifteen cases emphasises the histomorphologic criteria for diagnosis especially in the absence of mammographic picture, viz. a clinically palpable, well encapsulated mass which on histology shows normal breast epithelium admixed with fat, fibrous tissue and other mesenchymal elements. The epithelium in the hamartomas studied showed changes seen in normal breast especially in the progestational phase of the menstrual cycle. The stroma was either densely collagenous, hyalinised or cellular and admixed with fat in various proportion in thirteen cases, muscle in two cases and thick muscular arteries in four cases. It also showed pseudoangiomatous hyperplasia in seven cases. The importance of this change and probable evolution is discussed therein.
MAMMARY MYOFIBROBLASTOMA
Uncommon presentation of mammary myofibroblastoma. Hamele-Bena D, Cranor ML, Sciotto C, Erlandson R, Rosen PP. Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York 10021, USA.	Mod Pathol 1996 Jul;9(7):786-90 Abstract quote Myofibroblastoma, a rare benign mesenchymal mammary neoplasm, has been diagnosed largely in men as a unilateral, solitary lesion. We studied nine examples occurring in the breasts of eight patients, all but one of whom were women. In the man, the lesions were bilateral. Patients ranged in age from 44 to 67 years (mean and median, 55 yr). The tumors were well circumscribed and measured 0.9 to 3.0 cm (mean, 1.5 cm). They were composed of cells with a spectrum of appearances including small, compact cells, spindle cells, large histiocytoid cells, and epithelioid cells. All had broad bands of dense collagen, and adipose tissue was present in seven tumors. Foci of pseudoangiomatous hyperplasia were present in two cases. Strong vimentin positivity was present in seven tumors, which were cytokeratin negative. Weak S100 positivity was demonstrated in one lesion, and actin was positive in two lesions. Desmin was positive in six tumors and negative in one tumor. Treatment for all of the patients was excisional biopsy. Follow-up, available in five cases, was from 10 months to 6 years, 11 months (mean, 37 mo; median, 63 mo). All patients are alive and without evidence of disease. The clinical and pathologic characteristics of myofibroblastoma in women are similar to published data on the tumor in men. The tumors exhibit heterogeneous immunoreactivity for markers associated with myofibroblasts. Excisional biopsy is adequate therapy.

PROGNOSIS AND TREATMENT	CHARACTERIZATION
PROGNOSTIC FACTORS
Pseudoangiomatous hyperplasia of mammary stroma. Vuitch MF, Rosen PP, Erlandson RA.	Hum Pathol 1986 Feb;17(2):185-91 Abstract quote Grossly circumscribed, nonhemorrhagic breast masses consisting of mammary stromal proliferations that simulated vascular lesions were studied in nine women. Histologically, a striking pattern, which appeared to consist of complex inter-anastomosing channels lined by slender spindle cells, was present in the mammary parenchyma. The importance of this benign lesion, referred to as pseudoangiomatous hyperplasia of mammary stroma, is its distinction from angiosarcoma. The patients ranged in age from 22 to 52 years; all were premenopausal. Each presented with a palpable unilateral mass, measuring up to 7 cm in diameter. The patients were treated by excisional biopsy and remained well for up to 2.5 years after excision. One patient had two local recurrences within one year of the original excision, and a second patient had a local recurrence at 14 months. No patient had another concurrent or metachronous malignant tumor of the breast or other organ, and no abnormal hormonal status was found. Complete local excision appears to be adequate treatment. It remains to be determined whether this is a neoplastic process. However, there is no evidence that it is a precursor of angiosarcoma, and ultrastructural observations demonstrate that the spaces found in the lesion are not true vascular channels. Rather, they appear to arise by a process that involves disruption and separation of stromal collagen fibers. Since small foci of this change are common in hyperplastic breast tissue from premenopausal women, it is likely that the development of a discrete tumor with this pattern represents an exaggerated form of stromal hyperplasia.
TREATMENT
TAMOXIFEN
Tamoxifen in the management of pseudoangiomatous stromal hyperplasia. Pruthi S, Reynolds C, Johnson RE, Gisvold JJ. Division of General Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.	Breast J 2001 Nov-Dec;7(6):434-9 Related Articles, Books, LinkOut Tamoxifen in the management of pseudoangiomatous stromal hyperplasia. Pruthi S, Reynolds C, Johnson RE, Gisvold JJ. Division of General Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA. Pseudoangiomatous stromal hyperplasia (PASH) is a relatively uncommon histologic finding in breast specimens. The clinicopathologic spectrum of this disease entity can range from a focal nonsignificant microscopic finding to a dominant palpable breast mass. To confirm the diagnosis, a biopsy is required primarily to distinguish PASH from a low-grade angiosarcoma. The mammographic description of PASH is a round or ovoid, circumscribed or partially circumscribed mass. The sonographic feature is a hypoechoic mass. PASH is similar to a fibroadenoma in clinical and imaging features. Progressive breast enlargement associated with engorgement, cyclical breast pain, and burning sensation is of significant concern for some women. The management of the palpable mass and associated symptoms has included excisional biopsy, often leading to recurrent excisions and even mastectomy. This report documents an impressive response to tamoxifen in a patient with PASH presenting with breast enlargement, pain, and breast masses. To our knowledge, there are no reports on the use of tamoxifen or other selective estrogen receptor modulators in the management of this benign breast condition.