Case Report: Metachronous colon metastasis of clear-cell renal cell carcinoma seven years after radical nephrectomy

Colon metastasis from renal cell carcinoma (RCC) is rare and can remain diagnostically elusive when the lesion is predominantly intramural. In this case, we present a 66-year-old man with melena and anorexia. He had undergone left radical nephrectomy for stage I clear-cell renal cell carcinoma (ccRCC) seven years earlier. Computed tomography showed a 5.2 × 4.0 cm mass in ileocecal colon, causing ileal obstruction, with multiple pulmonary nodules. Serum CEA, CA 19-9, and AFP levels were within normal ranges. Colonoscopy described a friable hemorrhagic lesion near the ileocecal valve, but six biopsy specimens from two examinations showed only necrotic tissue. PET-CT findings supported malignancy, and right hemicolectomy was performed. Pathology identified a 5.5 × 5.0 cm clear-cell malignant tumor with full-thickness intestinal wall infiltration. Immunohistochemistry supported metastatic clear-cell RCC. No abdominal recurrence was detected one year later, but pulmonary nodules progressed and the patient died of pulmonary embolism two years after colectomy. This case underscores the need to consider metachronous RCC metastasis in bleeding or obstructing colonic masses after nephrectomy, even when endoscopic biopsy and serum tumor markers are non-diagnostic.