The location of premalignant colorectal polyps under age 50: a further rationale for screening sigmoidoscopy.

The incidence of colorectal cancer (CRC) among young adults has been dramatically rising, with guidelines for screening recently adjusted to start at age 45. However, knowledge of the precursor lesions is limited. We recently reported that 83% of CRC diagnosed under age 50 are left sided. Our aim was to analyze the location and histology of benign colorectal lesions found in a cohort of patients younger than 50, documenting the presence of advanced histology. We used the database in the Department of Pathology to retrospectively review the location and histology of all benign colorectal neoplasms in patients under age 50 submitted to pathology examination during 2006-2016. A total of 8364 lesions were examined from 4773 patients, and 3534 (65.5%) of the patients had only one polyp and the rest had multiple. Mean age was 41.9 years (range 16-49) while 3843 (72.8%) of the patients were between the ages of 40 and 49. In total, 4570/8364 lesions (54.6%) were distal to the splenic flexure. The most common pathology was tubular adenoma (63.7%), then hyperplastic polyps (16.6%), sessile serrated lesions (SSLs) (13.1%), and tubulovillous adenomas (6.3%). Tubulovillous adenomas, villous lesions, advanced adenomas, and adenomas with high-grade dysplasia were all predominantly left sided (left colon and rectum = 77.6%, 85%, 78.3%, and 87.6% respectively). Of the SSLs, 71.5% were in the right colon while 16.6% of hyperplastic lesions were right sided. High-risk advanced adenomas are predominantly left sided. This focuses attention on the rectum and left colon where carcinogenesis is strong in the young.