Apocrine carcinoma of the breast: Review

Apocrine carcinoma of the breast is a rare subtype of breast carcinoma, which only presents as 4% among patients with breast cancer. The percentage varies based on the diagnostic criteria used by each institution to classify apocrine carcinoma. Several confusing terms used in previous studies, including apocrine ductal carcinoma in situ (ADCIS), apocrine morphology in lobular carcinoma in situ (Apocrine LCIS), apocrine-like invasive carcinoma, pure apocrine carcinoma, molecular apocrine tumors (MATs), and triple-negative apocrine carcinoma of the breast (TNAC). The treatment, prognosis, and molecular profiles are also diverse. Pure apocrine carcinoma has stricter criteria for diagnosis, requiring more than 90% of cells showing apocrine morphology and classic IHC characteristics of ER-negative, PR-negative, and AR-positive in at least 10% of tumor cell nuclei. Research related to prognosis is diverse due to the difficulty of unifying the diagnostic criteria. Current evidence of treatment is geared toward the use of neoadjuvant chemotherapy and anti-androgen therapy when AR is present, accompanied by other treatments if biomarkers are present, such as HER2, PI3K, or CDK4/6. This article focuses on clearly summarizing different subtypes and management of apocrine carcinoma of the breast.