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

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.