A Renal Cyst Invaded by Infiltrating Renal Cell Carcinoma With Multiple Hypermetabolic Bone Metastases as the Initial Presentation.

Cystic renal cell carcinoma (RCC) refers to an indolent version of RCC composed predominantly of cysts, and it is associated with good prognosis. We showed the FDG PET/CT findings in a patient with multiple hypermetabolic bone metastases presenting with pain in the left shoulder and upper abdomen, who was later found to have cystic RCC. FDG PET/CT demonstrated hypermetabolic bone lesions and slight thickening of the renal cyst wall with light metabolism. This report indicates the risk of misdiagnosing cystic RCC as a renalcyst.