Mismatch Repair Proteins in Sporadic Colorectal Polyps

Colorectal cancers often arise from benign polyps. Adenomatous polyps and serrated polyps progress step by step to adenocarcinoma and change to malignant cancers. Genetic and epigenetic changes have relationship with specific stages in polyp-adenocarcinoma progression and colorectal cancer histopathological changes. In this study we applied immunohistochemistry (IHC) staining in sporadic colorectal polyps to assay functional status of MLH1, MSH2, MSH6, and PMS2 proteins. In this cross-sectional study we assessed all patients with sporadic colorectal polyps admitted and performed polypectomy in gastrointestinal department of Taleghani Hospital from 2004 to 2008. IHC was abnormal in 6.8%, 4.5%, 3%, and 4.8% for MLH1, MSH2, MSH6, and PMS2, respectively. In all cases with abnormal PMS2, MLH1 was abnormal, while the same story happened with abnormal MSH2 and MSH6 (p<0.001). IHC staining results showed significant differences according to polyp location, and mean age of the patient (p<0.05). Meanwhile, adenomatous polyps and serrated adenoma polyps showed significant differences when MLH1 and PMS2 were considered (p<0.05). IHC staining is suggested for serrated adenoma specially those in left colon. However, IHC staining for right-sided polyps may not have increased benefits for patient's management.