MRC1 and breast cancer: Breast carcinomas from carriers of pathogenic or likely pathogenic germline MMR variants (LS-BC, n = 20) were compared to breast carcinomas from patients shown not to carry the predisposing MMR gene variant of their families (NC-BC, n = 10) and to established LS-spectrum tumors from pathogenic MMR gene variant carriers (LS-OC, n = 16, and LS-CRC, n = 18) (Tables 1 and 2).