A Rare Collecting Duct Carcinoma With Widespread Metastasis Visualized by 18F-FDG PET/CT

Collecting duct carcinoma is a rare and highly aggressive renal tumor with a poor prognosis. The presence of metastasis is common at collecting duct carcinoma diagnosis, but widespread metastases involving multiple soft tissues are extremely unusual. Here, we describe a 65-year-old man presenting with fever and lower leg pain as the first and main manifestations. After receiving anti-infective therapy for over 6 weeks without improvement, 18F-FDG PET/CT revealed a primary renal carcinoma with widespread metastases. A biopsy from the tubercle of fascicular spinal muscle indicated a diagnosis of collecting duct carcinoma.