Testicular Metastasis from Urothelial Carcinoma of the Renal Pelvis Detected on 18 F-FDG PET/CT: A Rare Case

Renal pelvis carcinoma and renal cell carcinoma are known for their unpredictable metastatic behaviour. While lungs, liver, bones, and lymph nodes are common sites of spread, testicular metastasis is exceptionally rare. We report a 61-year-old male who presented with painless haematuria and was found to have a left renal pelvis mass with renal vein thrombus. Whole-body 18 F- Fluorodeoxyglucose (FDG) PET/CT demonstrated extensive metastatic disease involving the lungs, liver, adrenal gland, multiple nodal groups, vertebrae, and an unusual FDG-avid right testicular mass. Ultrasound-guided biopsy of a liver lesion confirmed metastatic carcinoma, with immunohistochemistry favouring a urothelial origin. This case highlights the value of FDG PET/CT in the comprehensive staging of advanced renal malignancies and emphasises awareness of rare metastatic sites such as the testis, which may significantly impact staging, prognosis, and therapeutic decision-making.