ESR1 and neoplasm: Recently, CMT has been shown to be classifiable into human molecular subtypes luminal A, luminal B, HER-2, and triple-negative/basal-like according to estrogen receptor alpha (ESR1α), progesterone receptor, and HER-2/ErbB-2 expression by immunohistochemistry in patient tumor tissue and by qRT-PCR in a cohort of well-characterized cell lines [10, 11].