Effect of microsatellite instability on histopathological parameters and prognosis in colon cancers

Purpose: The aim of this study was to compare the clinicopathological features, while evaluating the frequency of MSI, and the survival rates in these patients in our patient group with MSI and microsatellite stabil (MSS) colorectal carcinomas (CRCs).Materials and Methods: We retrospectively enrolled 146 patients who underwent colon resection between the years of 2014-2022. The expression of MSI status was evaluated by immunohistochemistry. The association of MSI status, presense of tumor-infiltrating lymphocytes (TILs), and tumor budding score with a patient’s survival was assessed by the Kaplan–Meier method and Cox regression analysis.Results: There were 104 (71.2%) MSS cases and, 42 (28.8%) MSI cases. 15 (10.3%) MSI tumors were found to be MSI-low, and 27 (18.5%) to be MSI-high. MSI tumors were significantly associated with younger patients (<50), earlier stage (T1-T2), right localization, lower rate of lymph node metastasis, presence of mucinous component and TILs response. The Cox-regression model revealed TILs, tumor budding score, and MSI are variables that significantly affect survival. The presence of TILs exhibited a protective effect (Hazard ratio (HR)=0.446), which decreased the mortality risk by 2.24 times for the follow-up period, while the presence of high TBS increased the risk of mortality by HR=3.22.Conclusion: This study revealed that patients with MSI CRCs may show unique clinicopathological features and should be evaluated using some guiding parameters that will improve survival.