Prat et al. [21] reviewed the concordance between surrogate IHC-based and PAM50-based intrinsic subtyping and found a discordance rate of 30.7%; only 62% of HR+ HER2− tumor samples that were IHC-based Luminal A cancers were genomically classified as Luminal A, while 34% of patients with IHC-based Luminal B tumors were genomically classified as Luminal A. Whitworth et al. [17] and Yao et al. [22] assessed the concordance of MammaPrint/BluePrint signatures with IHC-determined molecular subtypes and found a 22–25% discordance rate. The gene discussed is ERBB2; the disease is cancer.