PGR and breast cancer: MicroRNAs constituted the largest part of the small RNA pool, reaching 81.7, 77.8, 79.8, 77.9, 72.4, and 82.1% of all small RNA molecules detected in intact controls, TNBC, PR+BC, TNBC/DCP, PR+BC/CRIZ, and PR+BC/TOP samples, respectively (Table 1).