Sessile serrated adenoma

A sessile serrated adenoma (SSA) is a premalignant flat (or sessile) lesion of the colon, predominantly seen in the cecum and ascending colon.Low magnification micrograph of a SSA.Intermediate magnification micrograph of a SSA.High magnification micrograph of a SSA showing crypt branching. A sessile serrated adenoma (SSA) is a premalignant flat (or sessile) lesion of the colon, predominantly seen in the cecum and ascending colon. SSAs are thought to lead to colorectal cancer through the (alternate) serrated pathway. This differs from most colorectal cancer, which arises from mutations starting with inactivation of the APC gene. Multiple SSAs may be part of the serrated polyposis syndrome. SSAs, generally, are asymptomatic. They are typically identified on a colonoscopy and excised for a definitive diagnosis and treatment. The serrated polyposis syndrome (SPS) is a relatively rare condition characterized by multiple and/or large serrated polyps of the colon. Diagnosis of this disease is made by the fulfillment of any of the World Health Organization’s (WHO) clinical criteria. SSAs are diagnosed by their microscopic appearance; histomorphologically, they are characterized by (1) basal dilation of the crypts, (2) basal crypt serration, (3) crypts that run horizontal to the basement membrane (horizontal crypts), and (4) crypt branching. The most common of these features is basal dilation of the crypts. Unlike traditional colonic adenomas (e.g. tubular adenoma, villous adenoma), they do not (typically) have nuclear changes (nuclear hyperchromatism, nuclear crowding, elliptical/cigar-shaped nuclei).