BACKGROUND: The incidence of early-onset colorectal cancer (EoCRC), defined as CRC diagnosed at <
50 years of age, is increasing globally. However, only a few studies are reported from Japan, and the clinicopathological features of EoCRC in Japanese patients remain unknown. METHODS: We retrospectively investigated consecutive Japanese patients who were pathologically diagnosed with invasive CRC at our hospital from January 2015 to December 2021. Patients were categorized into those who were diagnosed with CRC at <
50 years (early-onset group) and ≥ 50 years (late-onset group) of age. We compared the clinicopathological findings between the two groups. RESULTS: The analysis included 731 patients. EoCRC was diagnosed in 46 patients (6.3% of all patients). Of them, 41.3% demonstrated a positive fecal immunochemical test (FIT) for CRC screening as a diagnostic opportunity, which was significantly higher than that in the late-onset group (p = 0.032). Rectal cancer was significantly more prevalent in the early-onset group compared to the late-onset group (45.7% vs. 26.4%, p <
001). No significant difference in the rate of clinical stage at presentation was found between the two groups. Furthermore, patients with positive FIT were more likely diagnosed at an earlier stage. CONCLUSIONS: EoCRC among Japanese patients tends to occur on the rectum and is more frequently diagnosed with FIT screening compared to late-onset CRC. Patients with advanced stage were diagnosed by symptoms, indicating the usefulness of FIT screening in diagnosing EoCRC at an early stage.