Pooling all of the expression of the genes in the classifier, ACTB, BLM, BUB1B, CCR1, CKAP5, CLCA2, DDX39, DTX2, ERBB2, ESR1, MKI67, OBSL1, PGR, PHACTR2, PIM1, PTI1, RCHY1, RPLPO, SF3B5, STIL, TFRC, TPX2, and YWHAB indicates an increased likelihood of breast cancer [26–28]; however, membership in a prognostic gene list is not necessarily indicative of a gene’s importance in cancer pathology. Here, ESR1 is linked to cancer.