Pseudoangiomatous hyperplasia of male breast.

Ninety-three male breast specimens have been examined for the presence of pseudoangiomatous hyperplasia of the mammary stroma which has hitherto been described almost exclusively in females. Forty-four cases (47.4%) showed some degree of hyperplasia, varying from small microscopic foci to extensive change involving 90% of the mammary tissue. All but one were found in association with gynaecomastia, early and intermediate stage. The association between pseudoangiomatous hyperplasia and benign proliferative lesions mirrors that reported in the female breast, and our findings suggest that the change may represent a stage in the maturation of newly formed mammary stroma.