Clinicopathological Features of Endoscopically Resected Early-Onset Colorectal Neoplasia Compared with Later-Onset Cases

<b>Background:</b> The incidence of colorectal cancer diagnosed before age 50 has been increasing worldwide. However, limited data describe the endoscopic and pathological features of colorectal lesions encountered and treated during routine colonoscopy in younger adults. This study aimed to characterize age-related differences in endoscopically resected colorectal neoplasia. <b>Methods:</b> We conducted a retrospective, single-center observational study of consecutively endoscopically resected colorectal neoplasia at a high-volume academic teaching hospital in Japan. Patient-level and lesion-level characteristics were compared between early-onset (<50 years) and later-onset (≥50 years) groups. Lesions were evaluated for location, morphology, size, histology, resection method, and advanced neoplasia status. <b>Results:</b> A total of 1299 patients with 3399 lesions were analyzed, including 498 early-onset patients with 940 lesions. Early-onset neoplasia showed a left-sided predominance, with higher proportions in the distal colon and rectum. Pedunculated morphology was more frequently observed in early-onset lesions. Early-onset disease was also associated with larger lesion size, a higher prevalence of high-grade tubular adenoma, and increased rates of advanced adenoma and advanced neoplasia, resulting in more frequent use of endoscopic mucosal resection or submucosal dissection. <b>Conclusions:</b> Endoscopically resected colorectal lesions in younger adults exhibit distinct anatomical and morphological features compared with later-onset cases, indicating heterogeneity at the premalignant stage.