Serrated carcinoma arising from a sessile serrated adenoma
11 April 2013 (online)
Sessile serrated adenoma/polyp (SSA/P), a distinct serrated polyp subtype, can progress to colorectal cancer via the serrated neoplasia pathway . On endoscopic examination, SSA/Ps usually show a flat or sessile appearance, a mucus covering, and a type II pit pattern. The endoscopic findings of uncomplicated SSA/Ps are well known; however, the endoscopic features of serrated carcinomas arising from SSA/Ps have not been fully described  . Herein, we report a case of serrated carcinoma arising from an SSA/P in a 66-year-old man who underwent endoscopic submucosal dissection (ESD) following colorectal cancer screening.
Colonoscopy revealed a 27-mm laterally spreading tumor in the ascending colon ([Fig. 1]). Most of the mass showed a flat elevated surface with a mucus covering, whereas the peripheral portion displayed a nodular appearance. The central area showed a type II (stellate) pit pattern, whilst the peripheral area displayed a type III (tubular) pit pattern ([Fig. 2]). Because there was a considerable risk of piecemeal resection, the tumor was resected by ESD instead of by endoscopic mucosal resection (EMR) .
On gross examination, the mass comprised two main parts ([Fig. 3 a]). Histopathological examination of these areas showed that the flat elevated area met the SSA/P criteria (green line), the nodular reddish area corresponded to an intramucosal adenocarcinoma (red line), whilst histologic transition was noted between the two areas (orange line; [Fig. 3 b, c]).
Despite increasing attention being paid to SSA/Ps, the endoscopic findings of SSA/Ps that are showing early neoplastic progression are not yet well known. We believe the present case clearly shows a biphasic endoscopic appearance of an SSA/P transitioning to a serrated carcinoma.
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