Adenomyoepithelioma of the breast with a distinctive type of apocrine adenosis.

A newly recognized type of dimorphic carcinoma of breast, distinct from adenoid cystic carcinoma, is described. It is characterized by a predominantly solid, clear cell myoepithelial proliferation, with centrally situated glandular lumina lined by apocrine cells. All cases arose in association with a distinctive type of atypical apocrine adenosis which has to be distinguished from microglandular adenosis and from tubular carcinoma. The biological behaviour of the tumour remains to be ascertained on the basis of longer follow-up, but it appears to have only limited malignant potential.