Clinicopathological Characteristics of Colorectal Neoplasia in Adults Younger than 50 Years: A Real-World Single-Center Study

Background: Colorectal neoplasia in adults younger than 50 years has attracted increasing clinical attention because of the rising incidence of early-onset colorectal cancer. However, the clinicopathological characteristics of colorectal lesions detected in younger adults remain incompletely described. This study aimed to characterize the clinical, anatomical, and histopathological features of colorectal neoplasia in adults younger than 50 years undergoing colonoscopy. Methods: This retrospective single-center study included adults aged 18–49 years who underwent complete colonoscopy between January 2018 and December 2023. After exclusion of individuals with normal colonoscopy findings, 152 patients with at least one colorectal lesion were included. Lesions were classified as benign, advanced, or malignant according to established histopathological criteria. Demographic, endoscopic, and pathological characteristics were analyzed and compared across lesion categories. Results: Among 152 patients, 83 (54.6%) had benign lesions, 64 (42.1%) had advanced neoplasia, and 5 (3.3%) had malignant lesions. Advanced lesions were observed predominantly in individuals aged 40–49 years. Most lesions were detected in symptomatic patients undergoing clinically indicated colonoscopy. Histopathological evaluation demonstrated a higher frequency of villous/tubulovillous adenomas, sessile serrated lesions, and high-grade dysplasia among advanced lesions. Larger lesion size was strongly associated with advanced pathological features (p < 0.001). In multivariable analysis, patients aged 30–39 years had significantly lower odds of advanced or malignant neoplasia than those aged 40–49 years, whereas no independent associations were observed for sex, smoking status, alcohol use, family history of colorectal cancer, or lesion location. Conclusions: In this selected cohort of adults younger than 50 years with detected colorectal lesions undergoing clinically indicated colonoscopy, advanced neoplasia represented a substantial proportion of cases. These findings should not be extrapolated to the general population of adults younger than 50 years or to screening cohorts.