Immunohistochemical study of MSH2, MSH6, PMS2, MLH1 in evaluation of differentiation grade of colon adenocarcinoma

Microsatellite instability is associated with dysfunction of the MSH2, MLH1, PMS2 and MSH6 genes, which participate in the repair of unpaired nucleotides of DNA. It is known that microsatellite instability is an independent prognostic factor in determining the differentiation grade of colon cancer. The use of immunohistochemistry to study the repair system of unpaired nucleotides has its own characteristics and limitations. Materials and methods. The study included 39 patients with colon adenocarcinoma. Moderately-differentiated colon adenocarcinoma was the most common histological type (72 %). There were 8 % of well-differentiated and 12 % poorly-differentiated carcinomas. Immunohistochemical analysis of SH2, MSH6, PMS2 and MLH1 proteins was done according to the standard protocol. Results. Out of 39 cases, 6 (15 %) had loss of expression of at least one of the studied proteins. Out of these 6 cases with indirect signs of MSI-H, 3 were poorly-differentiated, 1 was mucinous and 2 were moderately differentiated adenocarcinomas. Conclusion. Thus, immunohistochemical analysis of DNA repair genes can be used to determine the histological differentiation of colon adenocarcinoma.