Pseudoangiomatous
Stromal Hyperplasia (PASH)
Epidemiology and Etiology:
- Premenopausal
women usually
- post-menopausal
women on hormone replacement
- males with
gynecomastia
- may grow rapidly
during pregnancy
Common sites:
Gross features:
- firm, rubbery
- smooth outer
surface
- homogenous fibrous
tan on cut surface
Histologic features:
- anastomosing,
angulated, and slit-like spaces lined by slender spindle cells
- spaces are empty
or occasional RBC
- dense collagenous
background
- bland cytology
- no mitoses
- FNA:
- Non-diagnostic or
paucicellular specimen
Immunophenotype:
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Marker:
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Sensitivity:
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Specificity:
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Vimentin
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CD34
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Actin
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CD31 (neg)
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Uniformly
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Factor VIII (neg)
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Uniformly
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Molecular features:
Other features:
- EM –
myofibroblastic features
- Elongated cytoplasmic
processes
- Well-developed ER
- Prominent Golgi
- Collagen fibrils
in intervening stroma
- usually incidental
finding
- clinically
indistinguishable from fibroadenoma
- may locally recur
if incomplete excision
References:
- O’Malley’s Breast
Pathology 2006