Pseudoangiomatous stromal hyperplasia (PASH) of
the breast is a benign proliferation of mesenchymal cells
with irregular slit-like formations. The term is proposed to
emphasize the fact that the histological pattern mimics a
vasoformative proliferation[
1].
The age at diagnosis ranges from teenage to 50s[1].
The nodular PASH is typically well circumscribed and the
cut surface is pale, fibrous and homogenous. Macroscopically,
nodular PASH is usually indistinguishable from fibroadenoma ranging in size from 2 to 15 cm[1]. Histologically,
PASH can be mistaken for a low-grade angiosarcoma
but it can be distinguished by its growth pattern
and cytological features[2].
The origin of the cells which line up the slit-like spaces
is thought to be myofibroblasts. Therefore in addition
to CD34, positivity for smooth muscle actin, desmin and
calponin can be detected in these cells.
PASH can be identified in diffuse form or nodular
form. Microscopic foci of PASH can be identified in up to
23% of breast biopsies obtained for benign or malignant
conditions[3]. Most of the nodular cases are detected in
premenopausal women suggesting that hormonal factors
may play a role in its development.
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