ESR1 and neoplasm: Initially, PAM50 estimates for each tumour were compared with IHC-defined subtypes and overall good accordance was observed: luminal A samples were 89% IHC-defined ER-positive; 62% of basal-like samples were of the triple-negative phenotype (IHC-defined ER-negative, PgR-negative, and HER2-negative; TNBC); and 73% of HER2-enriched samples were IHC-defined HER2-positive among samples with available IHC status.