Primary Prostatic Synovial Sarcoma With Intravenous Tumor Thrombus Presented on 18 F-FDG and Al 18 F-Thretide PET/CT.

A 35-year-old man with painful and difficult urination underwent 18 F-FDG and Al 18 F-Thretide PET/CT scans after a pelvic MRI suggested a prostate mass. The 18 F-FDG and Al 18 F-Thretide PET/CT scans revealed a prostate mass accompanied by an intravenous tumor thrombus. Both the prostate mass and the intravenous tumor thrombus demonstrated increased FDG uptake. Intense PSMA activity was observed in both lesions, with the intravenous tumor thrombus showing considerably higher PSMA activity compared with its FDG uptake. Histologic analysis of the biopsy confirmed the diagnosis of prostatic synovial sarcoma. PSMA immunohistochemistry showed high PSMA expression in the vascular endothelial cells within the tumor.