Vascular leiomyosarcoma (LMS)is a rare malignant tumor arising from the muscle cells of the media of the vessels. Vascular LMS is often diagnosed as a result of the clinical manifestations of impaired venous flow such as edema and phlebothrombosis. The authors present a case of an LMS in a 72-year-old woman. Physical examination revealed a round mass deep in the left inguinal region close to the inguinal vessels, fixed and not pulsating. There was no sign of left lower-limb edema nor of articular impairment of the hip. Inguinal and distal pulses were normal. Results of laboratory analysis, including values for the oncologic markers, were normal. An ultrasound scan of the left inguinal fossa showed a 50-by-30 mm mass of mixed aspect that adhered to the left common iliac artery. An echo color Doppler showed conservative arterial flow. Thus, a thrombotic aneurysm of the left iliac artery was diagnosed. Chest x-ray showed no pathological findings. An abdominal computerized tomograph (CT) scan confirmed the location of the neoplasm and revealed a narrowing of the left iliac vein compressed behind the mass. The finding was interpreted as a colliquative lymph node. The patient underwent explorative laparotomy with midline incision. The finding was a neoplastic bilobed mass compressing and infiltrating the left iliac vein with no cleavage surface between the mass itself and the venous wall. An intraoperative frozen section revealed a necrotic mass with a cortex of ambiguous interpretation. Surgical procedure was then finished with no further venous resection. Histologic examination revealed the presence of leiomyosarcomatous tissue with nuclear pleomorphisms inside necrotic material limited by a thin fibrotic capsule. According to Coindre's classification the tumor was a G3. After six months the patient is fit and a CT scan showed no evidence of recurring disease.