Renal mass in sigmoid adenocarcinoma: clinical differential analysis of renal cell carcinoma versus metastasis

Abstract

Colorectal cancer remains a leading cause of cancer-related mortality, with more than half of cases being diagnosed at advanced or metastatic stages. Although the liver and lungs are the most frequent metastatic sites, renal involvement is exceedingly rare and may be misinterpreted as primary renal cell carcinoma (RCC). We present a case of a woman in her 50s diagnosed with stage IIIB sigmoid adenocarcinoma (cT3N1cMx) who underwent anterior resection followed by eight cycles of CapeOx. Post-treatment imaging demonstrated multiple hepatic metastases and a 1.8 cm lesion in the left kidney. Despite the recommendation for histopathologic confirmation, the patient declined biopsy. Given the clinical progression, second-line chemotherapy with FOLFIRI was initiated. The renal lesion was considered metastatic rather than primary RCC, supported by concurrent hepatic spread, prior colorectal cancer history, and radiologic characteristics. This case underscores the importance of considering renal metastasis in colorectal cancer and highlights the role of clinical and imaging evaluation when biopsy is not feasible.