Serrated polyps: clinical implications and future directions

Serrated polyps were once thought to have no clinical implications with regards to the development of colorectal cancer (CRC). Over the past several years, published data have enabled clinicians to develop a better understanding of these lesions. The serrated pathway associated with these lesions involves an epigenetic mechanism characterized by abnormal hypermethylation of CpG islands located in the promoter regions of tumor suppressor genes. It is often associated with BRAF mutations and may account for 15-35% of all CRC. This pathway may also play a major role in proximal neoplasia and missed cancer. There are three distinct subtypes of serrated neoplasia; hyperplastic (70% of all serrated polyps), sessile serrated adenoma/polyp (SSA/P) (25%) and traditional serrated adenoma (<2%). The last two forms are considered to be precursors for CRC. SSA/P are associated with synchronous CRC especially if the polyps are large (≥1 cm), multiple, or if they are in the proximal colon. Lesions containing serrated neoplasia are usually flat or sessile, may be large, and occasionally have a mucous cap. Serrated lesions provide many challenges for the clinician and may be difficult to detect and completely remove. Furthermore, pathologists may misclassify SSA/P as HP. For the first time, the Multi-Society Task Force guidelines for colorectal polyp surveillance have included the management of serrated lesions in their published recommendations. In addition, an expert panel has also recently issued recommendations regarding serrated neoplasia. In this article, we provide the reader with a summary as well as the latest developments regarding serrated colonic lesions.