The dark side of the colon: current issues surrounding the significance, prevalence, detection, diagnosis and management of serrated polyps.

Abstract

Hyperplastic polyps, once considered to have no malignant potential, are now recognized to be part of a larger group of polyps known as serrated polyps. Serrated polyps can progress to CRC through an epigenetic pathway known as CpG Island Methylator Phenotype (CIMP), characterized by hypermethylation of specific DNA regions such as the promoter regions of the DNA mismatch repair genes like MLH1. The CIMP pathway is tightly linked with mutations of the oncogene BRAF. There are three subtypes of serrated polyps - hyperplastic polyps, sessile serrated polyps (SSPs) and traditional serrated adenomas (TSAs). TSAs harbor cytologic dysplasia whereas hyperplastic polyps and SSPs are nondysplastic lesions. Currently, only SSPs and TSAs are believed to progress to CRC whereas hyperplastic polyps are thought to be benign with no malignant potential. This article will review the current evidence while highlighting some of the issues regarding serrated polyps. One challenge has been pathologically distinguishing hyperplastic polyps from SSPs, which is an important distinction, given the potential for progression of SSPs to CRC. Other challenges regarding serrated polyps include adequate detection and resection. Surveillance guideline recommendations for some serrated polyps have been changed in current guidelines to reflect the malignant potential, recommending closer surveillance intervals than the 10-year follow-up that has been traditionally provided for hyperplastic polyps. Given the difficulties in diagnosing as well as resecting, it is important for endoscopists to know how to detect, resect and manage follow-up in patients with serrated polyps.