The PAM50 gene signature measures the expression levels of 50 genes in a surgically resected breast cancer sample to classify a tumor as one of four intrinsic subtypes (Luminal A, Luminal B, HER2-enriched, and Basal-like) [15], which have been shown to be prognostic in both untreated (i.e. no adjuvant systemic therapy) and tamoxifen treated patient populations [15,16]. The gene discussed is ERBB2; the disease is neoplasm.