Vol. 4 Issue 3 Part A

Background: Identifying colorectal cancers (CRCs) with high levels of microsatellite instability (MSI-H) is clinically important. Few studies reported the role of histology in identifying MSI-H colorectal carcinomas. Hence the present study was undertaken to assess the value of histopathology in predicting MSI-H and its correlation with histopathologic prognostic features in CRC. Methods: Total 100 histo-pathologically confirmed cases of CRC were enrolled in the study. Tumour’s histopathological typing, staging, and sizing was conducted based on WHO criteria. Tumour grade, extent of mucin production, tumour growth pattern and presence of a Crohn’s like inflammatory infiltrate were determined. For immunohistochemistry (IHC) we used monoclonal antibodies (ES05 or 25D12). Results: Among 100 tumour samples, loss of MLH1 or MSH2 expression was detected in 13(13%) cases (MSI tumours) while 87(87%) tumours showed normal expression for MLH1 and MSH2 immuno-reactivity (MSS tumours). In terms of MSI/MSS status of tumour samples, statistical analysis showed that abnormal MMR protein expression was associated with tumour site, side of colon with cancer, size of tumour, tumour infiltrating lymphocytes and crohn’s like inflammatory infiltrate. Some histopathological and clinical features that appeared highly specific but much less sensitive in predicting MSI include stage, and some features were more sensitive and less specific which include tumour differentiation, CLR, TIL, dirty necrosis and pushing margin. Conclusion: MSI is an important prognostic factor in CRC and an important predictive factor of CRC chemotherapeutic treatment and outcome efficacy. Also result of the study is not consistent in describing various histopathological and clinical features in predicting MSI, CRC.