Clinicopathologic and endoscopic features of early-stage colorectal serrated adenocarcinoma

Abstract

Background: Serrated adenocarcinoma (SAC) is a distinct colorectal carcinoma variant that accounts for approximately 7.5% of all advanced colorectal carcinomas. While its prognosis is worse than conventional carcinoma, its early-stage clinicopathologic features are unclear. We therefore aimed to clarify the clinicopathologic and endoscopic characteristics of early-stage SACs.

Methods: Forty consecutive early-stage SAC patients at Hiroshima University Hospital were enrolled; SACs were classified into epithelial serration (Group A, n = 17) and non-epithelial serration (Group B, n = 23) groups. Additionally, we classified serrated adenoma into 4 types: sessile serrated adenoma (SSA), traditional serrated adenoma (TSA), unclassified, and non-serrated adenoma type.

Results: There were significant differences between Groups A and B in terms of tumor size (27.6 vs. 43.1 mm), incidences of T1 carcinoma (71% vs. 13%), and having the same color as normal mucosa (47% vs. 17%), respectively (p <0.01). In SACs >20 mm, the incidence of T1 carcinoma in Group A (70%) was significantly greater than that in Group B (13%) (p <0.05). There were significant differences in 'Japan NBI Expert Team' type 3 and type V pit pattern classifications between the 2 groups. The average TSA-type tumor size (42.6 mm) was significantly larger than that of the SSA (17.2 mm) and non-serrated component types (18.3 mm). The incidences of submucosal invasion in SSA- (80%), unclassified- (100%), and non-serrated-type (100%) tumors were significantly higher than that in the TSA type (11%).

Conclusions: Epithelial serration in the cancerous area and a non-TSA background indicated aggressive behavior in early-stage SACs.

Keywords: Colorectal cancer; Narrow band imaging; Pit pattern; Serrated adenocarcinoma.

Fig. 1

A case of Tis serrated adenocarcinoma with a serrated adenoma. a Colonoscopic view of a serrated adenocarcinoma lesion in the ascending colon. b Endoscopic findings after indigo carmine spraying; the small elevated nodule in the tumor can be observed. c Magnifying narrow-band imaging (NBI) observation. In the tumor lesion, mucosa with a Japan NBI Expert Team classification type B can be observed. d Magnifying endoscopic finding after indigo carmine dye spraying. Type II-open-containing normal type II pits are observed in the tumor. e Hematoxylin and eosin (HE) staining of the whole specimen. f, g High-power view of the HE-stain specimen; a section of adenocarcinoma is shown

Fig. 2

A case of T1 serrated adenocarcinoma without a serrated adenoma. a Colonoscopic view of serrated adenocarcinoma in the cecum. b Endoscopic view after indigo carmine dye spraying. A 0-Is lesion is clearly delineated. c Magnifying narrow-band imaging (NBI) observation; a Japan NBI Expert Team classification type 2B lesion can be observed. d Magnifying view of a crystal violet-stained section. e Hematoxylin and eosin (HE) staining of the whole specimen. f Immunostaining of the specimen with anti-desmin antibody; the muscle fibers are no longer visible. g High-power view of HE-stained specimen; epithelial serration is visible, and adenocarcinoma can be observed invading the submucosa