Objective  To investigate the expression and clinical significance of mismatch repair genes (MMR) MLH1, MSH2, MSH6, and PMS2 in colorectal carcinoma.

  Methods  Colorectal cancer tissues, collected from 607 patients enrolled in Sichuan Provincial People's Hospital from January 2015 to September 2016, were assigned into two groups based on whether the samples were positive or negative for MMR expression to determine the relationship between MMR expression and clinicopathology. We then evaluated the diagnostic value of MMR expression in the screening of Lynch syndrome and sporadic colorectal cancer.

  Results  The deletion rate of MMR protein was 35.58%. No statistically significant difference in age, sex, tumor size, P53, CD34, and D2-40 expression was detected between the negative group with MMR protein deficiency and the positive group with normal expression (P>0.05). Differences in tumor location, differentiation, TNM stage, lymph node metastasis, and VEGF and Ki-67 expression between the two groups were statistically significant (P < 0.05). The combined detection of MLH1, MSH2, PSM2, and MSH6 proteins may serve as a simple and economical method for screening patients with Lynch syndrome.

  Conclusions  The risk of colorectal cancer can be reduced by MMR detection of surgical specimens from colorectal cancer patients, screening of patients with Lynch syndrome and their family members, and assisting with proper management and intervention.