Primary colorectal cancer has been extensively studied due to the large number of cases, allowing for substantial insights into its clinical characteristics and treatment strategies. In contrast, metastatic colorectal cancer remains poorly understood because of its rarity and limited number of reports. With recent advancements in chemotherapy, accurately diagnosing metastatic lesions has become increasingly important and has significant implications for treatment planning. Here, we report the characteristics of 38 cases of metastatic colorectal lesions encountered at our institution.

We reviewed 38 patients who underwent colonoscopy at our institution between January 1, 2015, and October 31, 2025, and were diagnosed by biopsy pathology as having colorectal cancer originating from other organs. We analyzed the mode of invasion or metastasis, age and sex at diagnosis, indications for colonoscopy, cecal intubation status, lesion location, number of lesions, and endoscopic findings. Cases involving direct invasion from adjacent advanced tumors were classified as direct invasion, while those involving non-adjacent tumors were defined as distant metastasis.

The cohort consisted of 17 men and 21 women, with a mean age of 69.2 years. Indications for colonoscopy included screening in 15 cases, abnormal CT findings in 12 cases, bowel obstruction in 6 cases, and other reasons in 4 cases. Of the 38 cases, 17 were classified as direct invasion and 21 as distant metastasis. The cecal intubation rate was lower in the direct invasion group (9/17, 53%) than in the distant metastasis group (16/21, 76%). The most common primary tumor was of gynecological origin (15 cases), followed by gastric cancer (9 cases). Among gynecological cancers, 9 of 15 cases (60%) were direct invasion, whereas gastric cancer more commonly presented as distant metastasis (7 of 9 cases, 78%). Endoscopic findings in the direct invasion group mainly consisted of non-epithelial strictures or submucosal tumor–like protrusions. In contrast, the distant metastasis group displayed a wide variety of findings, including strictures, elevated lesions, flat lesions, and ulcers.

In cases of direct invasion, endoscopic findings predominantly consisted of strictures or SMT-like protrusions, and the cecal intubation rate was low. In contrast, distant metastasis demonstrated more diverse endoscopic appearances, ranging from protruding lesions to flat elevated lesions, and some cases were difficult to detect even on CT. When atypical endoscopic findings are observed in the colon of patients with another primary malignancy, we should consider the possibility of metastatic colorectal lesions.