Serrated carcinoma arising from a sessile serrated adenoma

Sessile serrated adenoma/polyp (SSA/P), a distinct serrated polyp subtype, can progress to colorectal cancer via the serrated neoplasia pathway [1]. 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 [2] [3]. 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) [4].

Fig. 1 Endoscopic image showing a 27-mm laterally spreading tumor in the ascending colon (arrows) with a mucus-covered surface that has a flat elevated appearance except for the peripheral portion, which displays a nodular surface.

Fig. 2 Endoscopic appearance after submucosal injection showing a type III (tubular) pit pattern in the nodular area and a type II (stellate) pit pattern in the flat area.

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]).

Fig. 3 Appearances of the resected tumor. a Gross appearance showing a biphasic tumor with a flat elevated area (green line), nodular area (red line), and an intervening transitional area (orange line). b Low power view of the tumor with the three areas indicated by their respective colors on the bar below (original magnification × 12.5). c High power view of each of the tumor areas showing features consistent with an SSA/P in the green area, an intramucosal adenocarcinoma in the red area and an area with low grade dysplasia in the transitional orange area (original magnification × 200).

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.

Endoscopy_UCTN_Code_CCL_1AD_2AB

Competing interests: None

• References

• 1 Snover DC. Update on the serrated pathway to colorectal carcinoma. Hum Pathol 2011; 42: 1-10
• 2 Huang CS, Farraye FA, Yang S et al. The clinical significance of serrated polyps. Am J Gastroenterol 2011; 106: 229-240
• 3 Rex DK, Ahnen DJ, Baron JA et al. Serrated lesions of the colorectum: review and recommendations from an expert panel. Am J Gastroenterol 2012; 107: 1315-1329
• 4 Lee EJ, Lee JB, Lee SH et al. Endoscopic treatment of large colorectal tumors: comparison of endoscopic mucosal resection, endoscopic mucosal resection-precutting, and endoscopic submucosal dissection. Surg Endosc 2012; 26: 2220-2230