[Colorectal serrated lesions: current insight on their role in colorectal carcinogenesis]

The classification of colorectal cancer precursor lesions has become more accurate after the discovery of serrated polyps. These are characterized by saw-tooth-like epithelial growth pattern, and are the most significant group of colorectal cancer precursors after conventional adenomas. While conventional adenomas are characterized by tumour suppressor gene mutations and chromosomal instability, serrated adenomas harbour KRAS/BRAF mutations, inhibition of apoptosis, DNA hypermethylation, and microsatellite instability. These alterations occur in about 20% of colorectal cancers, and along with preserved serrated morphology suggest their origin in serrated polyps. The recognition of serrated polyps as colorectal cancer precursors is crucial for their follow-up.