Specifically, using the estrogen receptor (ER), progesterone receptor (PR), and HER2 status of a tumor, breast subtype can be approximated as follows: luminal A (ER+ or PR+ and HER2–), luminal B (ER+ or PR+ and HER2+), HER2+/ER- (ER– and PR– and HER2+), and basal-like (ER– and PR– and HER2–) [7], [8]. The gene discussed is ESR1; the disease is neoplasm.