Breast
Other nonneoplastic
Pseudoangiomatous stromal hyperplasia
Authors: Indu Agarwal, M.D., Luis Blanco, Jr., M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Last author update: 21 April 2020
Last staff update: 20 September 2023 (update in progress)
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: Pseudoangiomatous stromal hyperplasia [TI] free full text[sb]
Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Sites | Etiology | Clinical features | Diagnosis | Radiology description | Radiology images | Prognostic factors | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Electron microscopy description | Sample pathology report | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Agarwal I, Blanco L. Pseudoangiomatous stromal hyperplasia. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastpash.html. Accessed September 30th, 2023.
Definition / general
- Benign myofibroblastic proliferation simulating a vascular lesion
- First described in 1986 (Hum Pathol 1986;17:185)
Essential features
- Benign myofibroblastic proliferation simulating a vascular lesion
- Usually an incidental finding but may produce palpable or mammographic mass
- Complex interanastomosing spaces in dense collagenous, keloid-like stroma
- Some of these spaces have spindle shaped myofibroblasts at their margins that simulate endothelial cells
- Spindle cells are positive for ER, PR and CD34 but negative for other vascular markers, e.g. CD31
Terminology
- Also called pseudoangiomatous hyperplasia of mammary stroma
- PASH is an incidental microscopic finding in up to 23% of breast surgical resections (Int J Surg 2011;9:20)
Epidemiology
- Almost always women who are premenopausal
- Also common in men with gynecomastia (Histopathology 1995;26:463)
- Also occurs in children (Pediatr Dev Pathol 2009;12:450)
Sites
- Breast stroma
Etiology
- Myofibroblastic origin, postulated role of hormonal factors (Arch Pathol Lab Med 2009;133:1335)
Clinical features
- Usually asymptomatic and an incidental finding but may be detected by imaging (Front Surg 2016;2:73, J Breast Health 2015;11:144)
Diagnosis
- Histologic examination of resected tissue
Radiology description
- May produce a mammographically detected mass
Radiology images
Contributed by Mark R. Wick, M.D.
Mammogram
Images hosted on other servers:
Round mass
Prognostic factors
- Nonneoplastic but mass forming lesion may rarely recur, especially in younger patients
Case reports
- 11 year old girl with bilateral nodular lesions (J Med Case Rep 2017;11:284)
- 12 year old girl with pseudoangiomatous stromal hyperplasia (Breast J 2007;13:603)
- 30 year old woman with pseudoangiomatous stromal hyperplasia of the breast with foci of morphologic malignancy (Int J Surg Pathol 2010;18:564)
- 37 year old woman with giant nodular pseudoangiomatous stromal hyperplasia of the breast presenting as a rapidly growing tumor (Chir Ital 2009;61:369)
- 46 year old woman with bilateral marked breast enlargement (BMJ Case Rep 2015;2015:bcr2014204343)
- 67 year old man with pseudoangiomatous stromal hyperplasia of breast (Breast J 2011;17:311)
Treatment
- Local excision needed only in symptomatic mass forming lesions
- If diagnosed on core needle biopsy, no surgical excision required, provided the diagnosis is concordant with radiologic findings (WHO Classification of Tumours Editorial Board: Breast Tumours (Medicine), 5th Edition, 2019)
Gross description
- Usually unilateral, well circumscribed, smooth nodule
- Cut surface is firm, gray-white, lacks the characteristic slit-like spaces of fibroadenoma
- No hemorrhage or necrosis (Schnitt: Biopsy Interpretation of the Breast (Biopsy Interpretation Series), 3rd Edition, 2017)
Gross images
Images hosted on other servers:
Well demarcated lesion
Microscopic (histologic) description
- Complex interanastomosing spaces in dense collagenous, keloid-like stroma
- Some of these spaces have spindle shaped myofibroblasts at their margins that simulate endothelial cells
- Spaces are usually empty but may contain rare erythrocytes
- Cellular areas or plump spindle cells may obscure pseudoangiomatous structure
- Often gynecomastia-like changes (Mod Pathol 2008;21:201)
- Associated with columnar cell lesion (Int J Clin Exp Pathol 2009;3:87)
- Rarely multinucleated giant cells (Breast J 2007;13:568)
- No mitotic figures, no necrosis, no atypia
- Fascicular PASH: cellular variant, in which myofibroblasts aggregate into fascicles with reduced or absent clefting, resembles myofibroblastoma
Microscopic (histologic) images
Contributed by Indu Agarwal, M.D.
Interlobular PASH
Slit-like spaces
Spindle cells lining the spaces
CD31
CD34
Cytology description
- Moderately cellular with cohesive clusters of bland ductal cells (occasionally with staghorn pattern), single naked nuclei, some spindle cells with moderate cytoplasm and fine chromatin
- Occasional loose hypocellular stromal tissue fragments containing spindle cells and paired elongated nuclei in fibrillary matrix (Acta Cytol 2003;47:373)
- Findings can confirm benign nature of disease but are nonspecific, resembling fibroadenoma or phyllodes tumor (Indian J Pathol Microbiol 2005;48:260)
- Finding plump spindled mesenchymal cells is suggestive (Diagn Cytopathol 2005;32:345)
Positive stains
- Spindle cells:
- PR (intense), ER-beta, androgen receptor, vimentin, CD34 (Am J Surg Pathol 1991;15:145, Int J Clin Exp Pathol 2009;3:87, Am J Surg Pathol 1995;19:270)
- Variable desmin and actin
Negative stains
- Spindle cells:
- Factor VIII, Ulex, CD31, keratin
Electron microscopy description
- Spaces are not true vascular channels but due to disruption and separation of stromal collagen fibers
Sample pathology report
- Left breast, at 5 o'clock and 4 cm from the nipple, ultrasound core needle biopsy:
- Breast tissue with pseudoangiomatous stromal hyperplasia
Differential diagnosis
- Low grade angiosarcoma:
- Hemorrhagic, soft, interanastomosing vascular channels containing red blood cells with invasion into breast parenchyma
- Papillary endothelial growth and hyperchromatic endothelial cells
- CD31+, factor VIII+ (Arch Pathol Lab Med 2009;133:1335)
- Myofibroblastoma:
- Neoplastic clonal tumors with characteristic genetic change (del 13q14) (this can be demonstrated by loss of Rb protein immunohistochemistry in myofibroblastoma)
- Solid mass of spindle cells which surrounds and involves ducts and lobules
- Other spindle cell tumors e.g. fibromatosis:
- Tumor cells arranged in long fascicles without significant clefting, nuclear beta catenin staining and CD34-
Additional references
Board review style question #1
- The finding shown in the image above was obtained on the core needle biopsy of the breast in a 35 year old woman. What is the most likely mammographic finding?
- Architectural distortion
- Calcifications
- Irregular mass
- Mass with smooth borders
- No abnormality, incidental finding
Board review style answer #1
E. No abnormality, incidental finding
Pseudoangiomatous hyperplasia is usually an incidental finding but may less commonly produce palpable or mammographic mass.
Comment Here
Reference: Pseudoangiomatous stromal hyperplasia
Pseudoangiomatous hyperplasia is usually an incidental finding but may less commonly produce palpable or mammographic mass.
Comment Here
Reference: Pseudoangiomatous stromal hyperplasia
Board review style question #2
- Which of the following set of immunohistochemical stains would be most suitable for the diagnosis of pseudoangiomatous hyperplasia (PASH)?
- CD34-, CD31-, ER-, nuclear beta-catenin+
- CD34-, CD31-, nuclear beta catenin+, AE1 / AE3+
- CD34+, CD31-, ER+, factor VIII-
- CD34+, CD31+, ER-, factor VIII+
Board review style answer #2
C. CD34+, CD31-, ER+, factor VIII-
The immunoprofile in option D is most consistent with angiosarcoma or other vascular lesions, with positive vascular markers. Option A is the immunoprofile for fibromatosis with positive nuclear beta catenin. It is important to note that fibromatosis is negative for CD34 as it does not arise from myofibroblasts. Option B is the classic staining pattern for a spindle cell carcinoma with positive AE1 / AE3.
Comment Here
Reference: Pseudoangiomatous stromal hyperplasia
The immunoprofile in option D is most consistent with angiosarcoma or other vascular lesions, with positive vascular markers. Option A is the immunoprofile for fibromatosis with positive nuclear beta catenin. It is important to note that fibromatosis is negative for CD34 as it does not arise from myofibroblasts. Option B is the classic staining pattern for a spindle cell carcinoma with positive AE1 / AE3.
Comment Here
Reference: Pseudoangiomatous stromal hyperplasia
