A 59 year old woman underwent excision for a breast density. Concern about the micropapillary epithelial proliferation was the reason for consultation.
Diagnosis: Usual hyperplasia without atypia, with epithelial and stromal changes similar to patterns seen in gynecomastia.
Discussion: The stromal fibrosis was responsible for the breast density. Although some of the stromal changes resemble pseudoangiomatous stromal hyperplasia (PASH), the changes are limited, and associated with a pattern of hyperplasia similar to that seen in men having gynecomastia. Thin, tapering micropapillae with occasional pyknotic nuclei are characteristic of this pattern of usual (non-atypial) hyperplasia.