A lactating adenoma of the breast.

A lactating adenoma of the breast was first examined at the 24th week of gestation, and had doubled in size by the 37th week. After delivery, administration of bromocriptine (5 mg/day) reduced its size, and it was surgically removed on the 10th day. Histologically, the glandular epithelial cells of the adenoma showed the physiological changes normally seen during lactation, and retained much of their lactating activity (especially protein secretion). The myoepithelial cells contained an increased number of lysosomes and also some autophagosomes, implying that the tumor had partly undergone involution similarly to the normal breast tissue.