Guided by the genomic information and the expression patterns of clinically defined ER, PR, and HER2 tumors, approximately 17% (183 cases) of TCGA breast cancer patients were diagnosed as having TNBC, with 55% being BL1 (64 cases, 35%) or BL2 (37 cases, 20%) subtypes [5]. Here, PGR is linked to breast cancer.