Answer: Gynecomastia

Histology: There are three morphologic features that are helpful in its recognition as male breast tissue with changes of gynecomastia. First, unlike the female breast, there is a conspicuous absence of lobules. Well-formed lobules are only occasionally noted in cases of gynecomastia. Second, in the more florid phases of gynecomastia the ducts manifest a characteristic micropapillary pattern of epithelial hyperplasia. Cells at the periphery of the ducts have abundant cytoplasm, while cells at the tips of the papillae have scant cytoplasm and hyperchromatic nuclei. Third, the periductal stroma is altered by the collection of edema.

Discussion: In the florid phase of gynecomastia, the epithelial proliferation may be quite pronounced and may even appear atypical with variable mitotic activity. This florid hyperplasia should not be mistaken for intraductal carcinoma. Although intraductal carcinoma may indeed arise in a background of gynecomastia, the atypical proliferations in florid gynecomastia are not believed to be associated with an increased risk for the subsequent development of carcinoma.