Patterns and characteristics of mismatch repair deficiency colorectal cancer from central China

Background: Up to 30% colorectal carcinoma (CRC) are inherited tendency. Lynch syndrome (LS) which is caused by mismatch repair (MMR) genes germline mutation, is the most prevalent form of hereditary CRC. Ethnical and regional differences would lead to diverse characteristics of LS. However, Studies of LS from China are few and with relatively small sample sizes. Method: Immunohistochemistry (IHC) testing for MMR deficiency (dMMR) is advocated to preliminarily screen LS in recent guidelines. This single center retrospective study from central China performed IHC to prescreen dMMR and analyze the patterns and characteristics of dMMR CRCs. Results: 12.0% (180/1505) CRCs had dMMR status in this study, they had the universal features such as younger diagnostic age, more proximal colon location, more poorly differentiated with an excess of mucinous type, advanced pT stage and lower pN stage (all P ＜ 0.05), but had larger tumor size and less perineural invasion (all P ＜ 0.05) compared with proficiency MMR CRCs, which were not reported before. Moreover, PMS2 deficiency (8.7%) was common in this study which was different from studies in Western. MLH1/PMS2, isolated PMS2, MSH2/MSH6 and isolated MSH6 were the most common deficiency patterns, and the MSH2/MSH6 subtype had the most often family history. Conclusion: This study demonstrated dMMR CRCs from central China had the similar general characteristics as reported studies, but had larger tumor size and less perineural invasion which were not reported before. What’s more, PMS2 deficiency (8.7%) was common in this study which was different from studies in Western.