This study aims to characterize the clinical and pathological features of early-onset colorectal cancer (EO-CRC; diagnosis at age ≤50) and to identify factors associated with more advanced tumor stage. The investigators will compare patients with early-stage disease (high-grade intraepithelial neoplasia, carcinoma in situ \[Tis\], and T1) to those with later-stage disease (T2 and above) to identify characteristics predictive of advanced staging. Adults aged ≤50 years with a pathological diagnosis of colorectal cancer or high-grade intraepithelial neoplasia at Shenzhen Hospital, Southern Medical University between January 2016 and September 2025 will be eligible for inclusion if clinical, endoscopic, and pathology records are available. This retrospective observational study will use existing medical records; no experimental treatments or additional procedures will be performed. De-identified information will be extracted from medical records, including demographics, symptoms, lifestyle factors, laboratory tests, endoscopic and imaging findings, pathology reports, treatments received, and follow-up outcomes. Data will be handled securely, stored using subject codes, and analyzed to compare groups and to develop statistical models that identify independent risk factors for advanced tumor stage. Participation involves no direct contact or additional testing for participants and poses minimal risk because only previously collected, de-identified data are used. Findings may inform improvements in early detection, risk stratification, and management strategies for younger patients with colorectal neoplasia.