Bilateral Diffuse Pseudoangiomatous Stromal Hyperplasia (PASH) Causing Gigantomastia in a 33-Year-Old Pregnant Woman: Case Report

Abstract

Pseudoangiomatous stromal hyperplasia (PASH) is a benign proliferation of mammary stroma mostly described as an incidental microscopic finding. Clinically, it can manifest as a palpable, well-circumscribed breast mass or in rare cases as a diffuse bilateral process causing massive breast enlargement. The most postulated theory for aetiology of this condition is hormonal stimulation of mammary myofibroblasts, particularly by progesterone. A definite diagnosis of PASH is based on typical pathological findings like stromal hyperplasia and empty slit-like channels positive for myofibroblastic and negative for endothelial markers. The main clinical differential diagnosis is a fibroadedoma or phylloid tumour, and histologically a low-grade angiosarcoma. There are less than 200 cases of tumorous PASH and less than 20 of diffuse PASH reported so far. Here we present a case report of huge diffuse PASH, that is, to our knowledge, the first in a pregnant woman.

Keywords: Breast; Diffuse pseudoangiomatous stromal hyperplasia; Mastectomy; PASH; Pregnancy.

Fig. 1

A Asymmetric breast enlargement within first trimester of pregnancy. B Painful skin ulcerations.

Fig. 2

Sagittal magnetic resonance imaging of the left breast, showing massive lymphoedema, distinctive thickening of the skin and subcutaneous tissue. There are no circumscribed mass lesions.

Fig. 3

A Skin-sparing mastectomy at 16 weeks of pregnancy. B Bilateral mastectomy specimens.

Fig. 4

Stromal hyperplasia and slit-like spaces (marked with arrows) lined by endothelial-like spindle cells.