The challenge of apocrine proliferations of the breast: a morphologic approach.

Apocrine phenotype in breast is common and can be seen in a broad spectrum of lesions ranging from simple cyst to infiltrating carcinoma. The majority of apocrine lesions of the breast are benign in nature and do not represent a diagnostic challenge; however, there are a few that can cause diagnostic problems, such as the case of apocrine proliferations with atypia and low-grade apocrine ductal carcinoma in situ. Furthermore, the role of atypical apocrine proliferations in the pathway to infiltrating carcinoma is still uncertain, and studies with long-term clinical follow-up are necessary to clarify and understand the significance of these apocrine lesions of the breast. The purpose of this article is to review the most recent literature concerning apocrine lesions, with emphasis on borderline apocrine proliferations.