Ultrastructural observations on gynecomastia.

Ten cases of gynecomastia were studied by electron microscopy. The ducts showed proliferation of both epithelial and myoepithelial cells. Intracytoplasmic lumina, previously thought to be a feature of malignant breast lesions, were seen. Squamous metaplasia was observed in some cases. The stroma showed fibroblasts, myofibroblasts, and, occasionally, pericytes. The general morphology of gynecomastia is similar to that of benign lesions of the female breast at the ultrastructural level. The features of the stromal cells reflect the effects of estrogenic stimulation.