ESR1 and breast carcinoma: We refer to data generated by Farmer et al. and Doane et al. as the "index cohorts." We use additional cohorts from Ivshina et al. [16], Rouzier et al. [17], and Sotiriou et al. [18], which contain 59, 51, and 34 ER- breast carcinoma samples, respectively, to confirm the existence of the molecular apocrine phenotype in larger cohorts outside the index cohorts and to explore gene network interactions.