Leiomyosarcoma of vascular origin: lessons learned from misdiagnosis

Leiomyosarcoma (LMS) of vascular origin is a rare entity of soft tissue sarcomas. Although they arise mostly from retroperitoneal major vascular structures, some encountered cases may arise from the smaller vascular structures of the thigh as the femoral vein. Due to their origin from the vascular structures, they represent a diagnostic challenge as they may be misdiagnosed as deep vein thrombosis (DVT). We present a case of a 45-year-old woman with left femoral and iliac vein LMS that was previously described in the vascular ultrasound (US) report as extensive DVT involving the femoral and external iliac veins. The patient did not improve after receiving the prescribed anticoagulants. Seven months later, the patient underwent computerized tomography (CT) with contrast, revealing a soft tissue mass in the anatomical site of the left common femoral and external iliac veins. The patient underwent both US-guided tru-cut biopsy and incisional biopsy from the iliac lymph nodes which revealed leiomyosarcoma. The patient underwent both vascular ultrasound and magnetic resonance imaging of the pelvis and the left thigh at the time of the first presentation. Seven months later, she underwent contrast-enhanced CT of the abdomen and pelvis. The patient was referred to the oncology department to receive the appropriate chemotherapy protocol as the tumor was inoperable. Although leiomyosarcoma of vascular origin is a rare entity of neoplasms, it is usually underestimated. A high index of suspicion would help the clinician to suspect such a neoplasm and save time for early diagnosis and management. Special caution should be taken for patients with venous thrombosis not improving on anticoagulants. When there is suspicion, other modalities such as computerized tomography and magnetic resonance imaging help confirm the diagnosis.