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Surgical Pathology Criteria

Pseudoangiomatous Stromal Hyperplasia


  • Microscopic or clinically apparent breast lesion of variable cellularity featuring dense collegenous stroma punctuated by slit like spaces

Alternate/Historical Names

  • Nodular myofibroblastic stromal hyperplasia of the mammary gland
  • PASH
  • Pseudoangiomatous hyperplasia of mammary stroma

Diagnostic Criteria

  • May be a circumscribed mass or microscopic incidental finding
    • Masses reported ranging from 0.8 - 11 cm
    • May be solitary or multifocal
  • Dense hyalinized collagen bundles
    • May expand intralobular stroma
    • Surrounds ducts and lobules
    • Usually circumscribed but merges with surrounding stroma
  • Anastomosing pseudovascular slit like spaces dissect through collagen bundles
    • No true vascular lining or structure
    • No erythrocytes in spaces
  • Spaces often lined by spindle cells with range of cellularity
    • Classically almost inconspicuous, discontinuous flat bland cells
      • One male case described with multinucleated cells
      • Classical areas also present in all cellular cases described
    • Spectrum of increased cellularity
      • Cells associated with spaces more numerous and larger
        • Nuclei may be larger and vesicular
      • Increased cellularity may obscure or obliterate pseuovascular spaces
      • May show marked cellularity with bundles and fascicles of cells
        • May predominate over collagenous stroma
    • CD34 positive but CD31 and Factor VIII negative
  • Rare cases described in ectopic breast tissue
    • Axillary and inguinal

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates: 5/1/06, 3/16/08, 3/6/12


Supplemental studies


CD34 16/17 positive
Vimentin 20/20 positive
Actin 12/19 positive
Desmin 4/20 positive
bcl2 Positive
PR Positive
ER Usually negative
CD31 Negative
Factor 8 Negative
S100 Negative
Keratin Negative

Differential Diagnosis

Low Grade Angiosarcoma Pseudoangiomatous Stromal Hyperplasia
Endothelial lined spaces No endothelial lining of spaces
Red blood cells in some spaces No red blood cells in spaces
Infiltrates fat No infiltration of fat
Infiltrates lobules Merges with lobular stroma
Lining is CD31+ Lining is CD31 negative
Both contain anastomosing spaces containing CD34+ cells


Myofibroblastoma Pseudoangiomatous Stromal Hyperplasia
Uniformly cellular Even cellular lesions have classical paucicellular areas
No epithelial elements within lesion Typically surrounds ducts and lobules
At the cellular end of the spectrum, PASH shows many features of myofibroblastoma and the pseudovascular spaces may be obscured; the two are probably morphologic variants of the same lesion


Perilobular Hemangioma Pseudoangiomatous Stromal Hyperplasia
Endothelial lined spaces No true lining to spaces
CD31 positive CD31 negative
Red blood cells in some spaces No red blood cells in spaces
Both are usually incidental findings


Hemangioma Pseudoangiomatous Stromal Hyperplasia
Endothelial lined spaces No true lining to spaces
CD31 positive CD31 negative
Red blood cells in some spaces No red blood cells in spaces


  • Age 10-67 years
  • In males, reported in 63% of cases of gynecomastia, ranging from microscopic to extensive
  • Female cases both palpable masses and microscopic lesions
    • Reported as an incidental microscopic lesion in up to 23% of specimens removed for other purposes in females
  • 5-10% of cases recur
    • None recurred aggressively or metastasized
  • Rare cases with multiple bilateral lesions


Breast Tumors with Vascular (and Pseudovascular) Differentiation

Breast Tumors and Lesions Exhibiting Reactivity for Muscle/Myoepithelial Markers

(Most benign lesions with an epithelial component will have a myoepithelial cell layer)


  • Vuitch MF, Rosen PP, Erlandson RA. Pseudoangiomatous hyperplasia of mammary stroma. Hum Pathol. 1986 Feb;17(2):185-91.
  • Powell CM, Cranor ML, Rosen PP. Pseudoangiomatous stromal hyperplasia (PASH). A mammary stromal tumor with myofibroblastic differentiation. Am J Surg Pathol. 1995 Mar;19(3):270-7.
  • Ibrahim RE, Sciotto CG, Weidner N. Pseudoangiomatous hyperplasia of mammary stroma. Some observations regarding its clinicopathologic spectrum. Cancer. 1989 Mar 15;63(6):1154-60.
  • Brogi E. Benign and malignant spindle cell lesions of the breast. Semin Diagn Pathol. 2004 Feb;21(1):57-64.
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  • Kazakov DV, Spagnolo DV, Stewart CJ, Thompson J, Agaimy A, Magro G, Bisceglia M, Vazmitel M, Kacerovska D, Kutzner H, Mukensnabl P, Michal M. Fibroadenoma and phyllodes tumors of anogenital mammary-like glands: a series of 13 neoplasms in 12 cases, including mammary-type juvenile fibroadenoma, fibroadenoma with lactation changes, and neurofibromatosis-associated pseudoangiomatous stromal hyperplasia with multinucleated giant cells. Am J Surg Pathol. 2010 Jan;34(1):95-103
  • Virk RK, Khan A. Pseudoangiomatous stromal hyperplasia: an overview. Arch Pathol Lab Med. 2010 Jul;134(7):1070-4.
  • Ruiz AN, Lima SP, Leite MS, Freitas R Jr. Breast pseudoangiomatous stromal hyperplasia during early childhood. Pediatr Int. 2011 Dec;53(6):1110-1 (abstract describes PASH in a 3 month old female, but I have not been able to review the full text yet)
  • Baker M, Chen H, Latchaw L, Memoli V, Ornvold K. Pseudoangiomatous stromal hyperplasia of the breast in a 10-year-old girl. J Pediatr Surg. 2011 Aug;46(8):e27-31
  • Jordan AC, Jaffer S, Mercer SE. Massive nodular pseudoangiomatous stromal hyperplasia (PASH) of the breast arising simultaneously in the axilla and vulva. Int J Surg Pathol. 2011 Feb;19(1):113-6.
  • Kazakov DV, Spagnolo DV, Kacerovska D, Michal M. Lesions of anogenital mammary-like glands: an update. Adv Anat Pathol. 2011 Jan;18(1):1-28
  • Drinka EK, Bargaje A, Ersahin CH, Patel P, Salhadar A, Sinacore J, Rajan P. Pseudoangiomatous Stromal Hyperplasia (PASH) of the Breast: A Clinicopathological Study of 79 Cases. Int J Surg Pathol. 2011 Aug 23. [Epub ahead of print]
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