Serrated Pathway to Colorectal Carcinogenesis: A Molecular Perspective

Serrated polyps of the colorectum are formed by a spectrum of lesions that share a unique histological feature- the presence of sawtooth-shaped crypts. In the last decade, significant advances have been made on deciphering the molecular differences between these morphologically similar lesions, which has paved path for our current understanding for their neoplastic potential. In particular, the sessile serrated adenoma has become to be recognized as the precursor lesion for the group of sporadic colorectal cancers with high levels of microsatellite instability. These recent findings have challenged the long-held fundamental paradigm that all colon cancers arise via the classic adenoma-carcinoma sequence. Although it is welcome news that we now better understand the molecular pathogenesis of some proportion of sporadic cancers, nonetheless serrated polyps present with a major challenge for the early detection and management of colorectal cancer, which is no longer considered to be a homogenous entity.