Molecularly defined apocrine carcinomas include tumors that share some common expression characteristics with the HER2+ group (ER-/PR-/HER2+) in the Stanford classification as well as with some lesions that exhibit features of the basal-like/triple negative group (high grade lesions; ER-/PR-/HER2-). The gene discussed is ESR1; the disease is apocrine adenocarcinoma.