RB1 and breast cancer: Mote et al.69 analyzed PR expression in tissue samples of 39 breast cancer patients and found that PR-A > PR-B accounted for 39% (15 out of 39 patients) cases, PR-A = PR-B accounted for 51% (20 out of 39 patients) cases, and PR-A < PR-B accounted for only 10% (4 out of 39 patients) cases.