In terms of the tumor characteristics, most of the breast cancers from MMR variant carriers were invasive ductal carcinomas, while MMR variant carriers might have more medullary [6.7% (1/15) vs. 0.6% (47/8070), p = 0.08] and papillary (13.3% (2/15) vs. 0.3% (23/8070), p < 0.001] carcinomas compared with non-carriers (Table 2). Here, MRC1 is linked to invasive ductal breast carcinoma.