Abstract
Leiomyosarcoma is an aggressive soft tissue tumor originating from smooth muscle cells typically of the uterus, gastrointestinal, or genitourinary system. The most common site of leiomyosarcoma of soft tissue is the retroperitoneum, accounting for 50% of all cases. The majority of patients are asymptomatic, which may be due to the large retroperitoneal cavity. However, when symptoms do occur, they are vague in nature. The most common growth pattern is an entirely extravascular mass. We are presenting an interesting case of a 65-year-old lady, who was referred to our hospital as a case of large left retroperitoneal mass with left renal vein thrombosis. She was biopsied and diagnosed with leiomyosarcoma with invasion into descending colon and the left renal vein, which led to renal vein thrombus. In the last few decades, there is a lack of studies about leiomyosarcoma invading the renal vein and Inferior Vena Cava (IVC). As far as we know, the leiomyosarcoma of a major blood vessel is extremely rare. Since leiomyosarcoma often has a late presentation with the advanced stage when detected, a high index of suspicion is needed to be detected early and avoid such a complication.