Evaluating the frequency of MLH-1 Loss in serrated polyps of colon: a single center study from Southern Iran

Aim: Evaluation of the role of MLH-1 loss in serrated polyps of colon in a population of South of Iran. Background: There has been extensive change in classification and pathogenesis of serrated polyps of the colon during the last 10 years. The new classification is mostly based on the knowledge of the molecular pathogenesis and the rate of progression to colorectal cancer in these types of polyps. One of the most common and early lesions in molecular pathogenesis of serrated colorectal cancer is loss of MLH-1. Patients and methods: In this study over 2 years (2012-13), 78 cases of colorectal polyps with serrated morphology resected in hospitals affiliated with Shiraz University of Medical Sciences were reclassified and investigated for MLH-1 loss by immunohistochemical method. Results: Out of the 78 colorectal polyps, 64 were classified as hyperplastic polyp (HP) and 14 as sessile serrated adenoma/polyp (SSA/P). There was no case of traditional serrated adenoma. Three cases of SSA/P located in right colon showed dysplasia. MLH-1 loss was detected only in these 3 cases. No case of HP or SSA/P without dysplasia showed MLH-1 loss. Conclusion: SSA/P is not a common serrated polyp in our population, i.e. it is much less common than HP. Although MLH-1 loss in serrated polyps of colon is overall rare, it is fairly common in dysplastic right sided SSA/P, which confirms this molecular change as an early event in serrated carcinogenesis .