Utility of C-Kit Expression by Immunohistochemistry as a Prognostic and Theranostic Marker in Colorectal Carcinoma

Objectives: Targeted therapy is now available for various carcinomas with growth factor receptor mutations. C-Kit, a tyrosine kinase receptor is overexpressed in many epithelial malignancies. The aim of this study is to determine the role of c-Kit (CD117) expression by Immunohistochemistry (IHC) in colorectal carcinoma (CRC) and to correlate the same with tumor grade, stage, nodal status and metastasis. Methods: This is a retrospective study conducted on paraffin blocks of histopathology proven CRC. Monoclonal antibody detected against c-kit antigen was observed in the cytoplasm and epithelial membrane of the tumour cells and c-Kit expression was given a score based on staining intensity and percentage of cells showing positivity. A statistical analysis using chi square test was performed to find any difference between the various tumor grade, stage, nodal status and metastasis with respect to their c-kit expression by IHC. Results: c-Kit was negative in 55% of the cases and out of 45% positive cases 3+ positivity was noted in 5% of the cases only. 2+ positivity was seen in 9% and 1+ in 31%. Statistical data showed a p-value of 0.96, 0.70, 0.48 and 0.68 for grade, stage, nodal status and metastasis of the tumor with respect to c-kit expression respectively. Conclusion: C-kit expression by IHC has only a limited role and is statistically not significant as a prognostic or theranostic marker in CRC. Molecular analysis of the tyrosine kinase receptor mutation is needed to determine its aberrant expression.