RADIOLOGY: GENITOURINARY: GU: Case# 34016: ?PROSTATE LYMPHOMA OR SARCOMA. 32 year old black male who has a known retroperitoneal mass obstructing the right ureter. Large heterogeneous pelvic mass is noted and has a differential diagnosis of a sarcoma such as leiomyosarcoma, a lymphoma, and a small cell carcinoma of the prostate or prostate sarcoma. A colon cancer is felt less likely due to the lack of metastatic disease in a tumor of this size. 2. Mass is causing bilateral deep venous thrombosis in the iliac vessels as well as bilateral ureteral obstruction. 3. Right groin lymphadenopathy is noted consistent with the mass with no focal abscess seen with the drain in good position.