Metastatic renal clear cell carcinoma to the rectum, lungs, ilium, and lymph nodes: A case report

BACKGROUND: Renal cell carcinoma metastasizing to rectum is very rare, and the unusual metastatic sites should be paid attention to during the follow-up of renal cell carcinoma. CASE SUMMARY: We describe a case of a 65-year-old male who was diagnosed with metastatic renal cell carcinoma to rectum 10 years after the right radical nephrectomy. Histopathology and immunohistochemical examinations contribute to making differential diagnosis between rectal metastasis of renal cell carcinoma and primary rectal clear cell carcinoma. Positron emission tomography-computed tomography with fluorodeoxyglucose shows hypermetabolic activity in upper rectum and other sites of metastasis at the same time. CONCLUSION: Possibility of unusual metastatic sites of renal cell carcinoma such as rectum indeed exists, which should not be ignored in the surveillance after resection of the primary tumor.