Abstract:ObjectiveTo investigate the clinicopathological significance of colorectal cancer with mesenteric tumor deposit(TD) and the relationship with DNA mismatch repair(MMR) protein expression. MethodsThe clinicopathological characteristics of 393 patients with colorectal cancer in the First Affiliated Hospital of Guangxi University of Chinese Medicine from January 2018 to December 2021 were retrospectively analyzed, all patients were diagnosed with postoperative pathology and the MMR proteins (MLH1, MSH2, MSH6, PMS2) were detected by immunohistochemistry. The patients were divided into the deficient mismatch repair (dMMR) group and proficiency mismatch repair(pMMR)group. According to the number of mesenteric TD, all the patients were divided into TD-negative group, TD-positive group （≥1）. The differences between the groups were compared. ResultsThere were 40 cases (10.2%) in dMMR group, 353 cases (89.8%) in pMMR group, 331 cases (84.2%) in the TD-negative group, 62 cases (15.8%) in the TD-positive group. TD is related to tumor grading, T stage and lymph node metastasis (P<0.05), and did not related to gender, age, location, etc(P>0.05). MMR protein expression was related to age, tumor grade, and whether mucinous adenocarcinoma (P<0.05), and did not related to tumor T stage, lymph node metastasis, distant metastasis, and TD (P>0.05). ConclusionsMesenteric TD is an indicator of poor prognosis of colorectal cancer，and may be equivalent metastatic-positive lymph nodes to staging in non-mucinous adenocarcinoma. Loss of MMR proteins expression is an important cause of juvenile, low-differentiation, mucotic colorectal cancer.