MSH2 germline mutation carriers with blood group type B had a 3.5-times higher risk of CRC (95% CI = 1.11–10.9) than those with blood group type O. However, regular physical activity was associated with a decreased CRC risk for MLH1 germline mutation carriers (HR = 0.52, 95% CI = 0.29–0.92). This evidence concerns the gene MSH2 and colorectal carcinoma.