DNA Mismatch Repair Deficiency in Colorectal Adenocarcinoma and its Association with Clinicopathological Features

Background: Evaluation of mismatch repair (MMR) status in colorectal cancer (CRC) could be used as the guidance for postsurgical treatment. Defective MMR status is associated with distinct clinicopathological features. This study aims to evaluate associations between MMR status and clinicopathological features in a retrospective cohort of consecutive Chinese CRC patients. Methods: Clinicopathological information was collected from 481 consecutive individuals who underwent curative surgery for CRC. MMR status was determined by Immunohistochemistry (IHC) staining, which was used to examine expression of MLH1, PMS2, MSH2 and MSH6 on paraffin embedded tissues containing adenocarcinoma. Results: IHC results showed that 33 (of 481, 6.9%) CRC cases presented loss of MMR proteins expression, including 26 (of 205, 12.7%) from colon and 5 (of 262, 1.9%) from rectum. Tumors with deficient DNA mismatch repair (dMMR) status were significantly related to younger patients, larger tumor size, mucinous-focal or signet-ring histological phenotype, and preferred right-sided location (P<0.001). And dMMR tumors also implied poor differentiation and more occurrence in stage CRC patients. No significant association was found between MMR status and gender, invasion depth and lymph node metastasis. Conclusions: We concluded that the prevalence of abnormal MMR protein expression in this cohort of Chinese CRC patients was comparable with the West. Meanwhile, tumors with dMMR status were associated with distinct clinicopathological characteristics of CRC patients.