Pathologic Predictors of Microsatellite Instability in Colorectal Cancer

Identification of microsatellite unstable (MSI-H) colorectal cancers (CRCs) is important not only for the identification or hereditary nonpolyposis colorectal cancer syndrome but also because MSI-H CRCs have. a better prognosis and may respond differently to 5-Florouracil-based chemotherapy. We present 2 nearly equivalent logistic regression models for clinical use that predict microsatellite instability based on the review of 1649 CRCs front patients of all ages collected in a population-based case control study in northern Israel. One hundred ninety-eight of these 1649 tumors demonstrated it high degree of microsatellite instability (12%). Multivariate analysis Found that > 2 tumor-infiltrating lymphocyte (TIL) cells per high-powered field, the lack of dirty necrosis. the presence of it Crohn-like reaction, right-sided location, any mucinous differentiation (mucinous or focally mucinous) and well or poor differentiation, and age less than 50 were all independent predictors of MSI-H. We developed 2 logistic regression models that differ only by the statistical approach used to analyze the number of TIL cells per high-powered field, where the slightly more accurate (and complex) model uses the log of the total number of TIL cells. The simpler clinical model uses it cut-off of 2 > TIL cells per high-powered field. The accuracy of both models is high. with an 85.4% versus 85.0%, probability of correctly classifying tumors as MSI-H. By employing the simpler model, pathologists can predict the likelihood of microsatellite instability by compiling the MSI probability score (Table 4 and Fig. 1) from simple histologic and clinical data available during sign-out. Our model shows that approximately 43% of CRCs have a MSI probability score of 1 or less and hence have little likelihood ( < 3%) of being MSI-H. Although this model is not perfect in predicting microsatellite instability. its use Could improve the efficiency of expensive diagnostic testing.