Comparison of malignant potential between serrated adenomas and traditional adenomas

Background:  Serrated adenoma is a discrete colorectal epithelial neoplastic lesion that can evolve into colorectal cancer. However, the degree of malignant potential has not been firmly established as yet. The purpose of the present paper was to compare the malignant potential and clinicopathological features between serrated and traditional adenomas. Methods:  A total of 124 serrated adenomas from 116 patients were assessed, and 419 traditional adenomas from 200 were randomly selected. The combination of nuclear dysplasia and serration of ≥20% of crypts was regarded as serrated adenoma. The clinicopathological features of serrated and traditional adenomas were compared, and multivariate analysis performed to confirm whether the malignant potential of serrated adenoma was similar to that of traditional adenoma. Results:  The differences in age, sex, total number of adenomas, and synchronous lesions including adenoma with high-grade dysplasia and carcinoma between subjects with and without serrated adenoma were not significant. Serrated adenomas were more frequently located in the rectum and sigmoid colon (P < 0.001), and the average size of serrated adenomas was greater than that of traditional adenomas (P < 0.05). The incidence of malignant lesions including high-grade dysplasia and carcinoma in serrated adenomas was found to be lower than in traditional adenomas (3.2% vs 9.3%, P < 0.05). In the multivariate analysis, adenoma type and polyp size constituted the risk factors for the incidence of high-grade dysplasia and carcinoma. Conclusions:  Serrated adenoma is a premalignant lesion, but it has a lower potential for the development of malignancy than traditional adenomas.