Delayed Metastasis of Clear Cell Renal Carcinoma to the Colon in the Setting of Benign Kidney Disease.

Clear cell renal carcinoma (CCRC) is a common variant of renal cell carcinoma (RCC), which presents with unpredictable features. The occurrence of RCC in those with autosomal dominant polycystic kidney disease (ADPKD) is debated. Most studies agree that ADPKD does not increase the risk of RCC; however, it makes diagnosing RCC difficult due to the nature of the disease. RCC frequently metastasizes to the lungs, lymph nodes, bones, liver, adrenal glands, and brain, but rarely metastasizes to the colon. In all previous reports, primary RCC was already diagnosed in the kidneys; thus, metastatic CCRC to the colon has never been described in the current literature in the absence of a primary renal tumor. Here, we report a rare presentation of metastatic CCRC wherein a patient with ADPKD presented with an obstructing sigmoid mass six years after bilateral nephrectomy for pathologically benign cysts. Despite a close follow-up after nephrectomy, our patient's non-specific symptoms were attributed to underlying comorbidities and more likely etiologies of back pain, diarrhea, and anemia, thus delaying and complicating the diagnosis of CCRC which subsequently led to metastases at the time of presentation. Although past literature has described CCRC metastases to other parts of the gastrointestinal tract or even described primary clear cell carcinoma of the colon, this is the first case in which a patient with benign cystic renal disease developed CCRC presenting as metastatic disease of the colon, rectum, liver, and lung. This paper will address the manifestations of ADPKD and postulate mechanisms for the unpredictable nature of this patient's RCC metastasis.