Traditional serrated adenoma (TSA) is a rare and precancerous lesion of colorectal cancer. The clinical and endoscopic differentiations between TSAs without dysplasia or adenocarcinoma (TSAOs) and TSAs with dysplasia or adenocarcinoma (TSADs) remain unclear.

To evaluate the characteristics of colorectal TSAs and compare the characteristics of TSAOs with those of TSADs.

This retrospective study included 193 patients who underwent endoscopic resection and received a pathologic diagnosis of TSA. We reviewed the medical, endoscopic, and histopathologic records of patients who underwent endoscopic resection of TSAs between January 2010 and December 2023.

TSAs were more frequently located in the rectosigmoid colon. Most TSAs had 0-Ip, 0-Isp, or 0-Is morphologies. The TSAD lesions were larger than TSAO lesions. TSAD lesions more commonly had a red color and an irregular border than TSAO lesions. TSAOs were usually treated using conventional endoscopic mucosal resection, whereas TSADs were treated using conventional endoscopic mucosal resection, endoscopic submucosal dissection, and surgery. Post-polypectomy bleeding was more common with TSADs than with TSAOs. Univariate analysis showed that gastrointestinal bleeding, red color, 0-IIa, irregular border, and lobular mucosal surface were significantly associated with TSADs. Multivariate analysis showed that gastrointestinal bleeding, an irregular border, and a lobular mucosal surface were significantly associated with TSADs.

TSAs with gastrointestinal bleeding, an irregular border, and a lobular mucosal surface are associated with an increased risk of dysplasia or adenocarcinoma.

Serrated polyps are classified into hyperplastic polyps, sessile serrated adenomas/polyps, and traditional serrated adenomas. Although all serrated polyps share characteristic colonic crypts serrations, distinguishing hyperplastic polyps from sessile serrated adenomas/polyps is challenging. Traditional serrated adenomas are cytologically dysplastic lesions; sessile serrated adenomas/polyps develop cytologic dysplasia as they progress to colorectal cancer. A flat and pale appearance of serrated polyps may make detection difficult. Endoscopic mucosal resection has higher rates of complete resection. Close surveillance is recommended for sessile serrated adenomas/polyps, sessile serrated adenomas/polyp with dysplasia, hyperplastic polyps ≥10 mm, and traditional serrated adenomas.