Sessile serrated adenomas (SSAs), characterized by the saw-toothed appearance of the colonic crypts, form and progress to colorectal cancers (CRCs) via a different pathway than conventional adenomas and are thought to contribute to 20% to 35% of all cases of CRC. Although little is known about their pathogenesis, endoscopists must be aware of the unique features of SSAs to efficiently detect and remove them during colonoscopy. In the January issue of Clinical Gastroenterology and Heptology, Seth D. Crockett et al review the history, epidemiology, and pathology features of SSAs, discussing management approaches and important areas for future research.
The World Health Organization recognizes 3 categories of serrated polyps, characterized by serration of the glandular epithelium: SSAs (also known as the sessile serrated polyps or lesions), traditional serrated adenomas, and hyperplastic polyps.
These progress to CRC along the serrated pathway, which involves BRAF mutation, CpG island methylation, epigenetic inactivation of the mismatch repair gene MLH1, and microsatellite instability (see figure).
Crockett et al emphasize that it is important for clinicians and researchers to recognize the importance of SSAs and their large contribution to interval cancers. Crockett et al state that unless gastroenterologists direct their attention to the detection, removal, and appropriate surveillance of SSAs, it will not be possible to optimize prevention of sporadic CRC.