[Pseudoangiomatous hyperplasia of mammary stroma]

Four cases of pseudoangiomatous hyperplasia of mammary stroma (PAH) were described (3 women and 1 man aged 15 to 42 years). Clinically in women, they presented as firm, nontender, movable nodules, 1 to 4 cm in diameter, diagnosed clinically usually as fibroadenoma. In the male patient, the lesion was tender, resembling gynecomastia. Microscopically, they were characterized by the presence of anastomosing, empty-looking, slit-shaped spaces irregularly lined by the spindle cells with small, uniformly ovoid nuclei, dispersed throughout the mammary stroma. Immunohistochemically, these cells were vimentin positive, factor VIII and CD31 negative. They did not express estrogen receptor, in one case there was a weak progesteron receptor positivity. Ultrastructurally, the lining cells were of a fibroblastic character. The pathogenesis of PAH is unclear, presumed to be of reactive nature by the authors, probably as an exuberant reaction of stromal cells to hormonal stimuli. In differential diagnosis, PAH should be distinguished from low-grade angiosarcoma, as well as from perilobular hemangioma, diffuse angiomatosis and vascular anomalies.