Immunohistochemical Analysis of Mismatch Repair Proteins in Iranian Colorectal Cancer Patients at Risk for Lynch Syndrome

Background: hereditary non-polyposis colorectal cancer (hnpcc) is a common hereditary cancer predisposing syndrome has molecular and clinicopathological features still have remained ambiguous within iranian populations. we discuss in this article some molecular and clinicopathological features of the condition.methods: the study was a descriptive retrospective and designed on 1659 colorectal cancer (crc) patients were screened based on early-onset disease and amsterdam ii criteria during 14 years (2000-2013). immunohistochemistry (ihc) staining was set up to detect expression of mismatch repair (mmr) genes on paraffin-embedded tissue sections of 31 hnpcc-crc tumors. spss 19 software was used to analyze the data.results: ihc-mmr staining was absent in 7/31 individuals (22.6%) of which 4 cases showed ihc-absent (ihc-a) in both msh2 and msh6 (57.1%), in 2 cases both mlh1 and pms2 had negative staining (28.6%), and just in one case, msh6 was defective (14.3%). the frequency of crc among ihc-a and ihc-present (ihc-p) families was 67.5% and 27.9%, respectively. also the most frequent extracolonic cancers in ihc-a group were: stomach (10%), small bowel (5%), and prostate (5%); and in ihc-p group: stomach (18.4%), lung (10.9%), and breast (7.5%). average age of ihc-a individuals at diagnosis was 38.0 versus 45.3 years in ihc-p individuals. overall, 20.8% and 57.1% of our index crcs were localized proximal to the splenic flexure in ihc-p and ihc-a groups, respectively.conclusion: given the lack of enough information about molecular aspects of hereditary cancer syndromes like hnpcc in iran, more evaluations are necessary on larger samples using complementary techniques such as msi-testing and mutation analyses.