From the METABRIC cohort (supplementary material, Table S1), low CYP2S1 mRNA expression was significantly associated with positive progesterone receptor (PgR) (χ2 = 10.400, df = 1, p = 0.001), HER2‐negative status (χ2 = 11.652, df = 1, p = 0.001), and luminal A cancers (χ2 = 15.377, df = 5, p = 0.009). The gene discussed is ERBB2; the disease is cancer.