Primary leiomyosarcoma originating from the deep femoral vein initially presenting as chronic deep vein thrombosis: A case report and review of literature.

Leiomyosarcoma (LMS) is a rare and aggressive smooth muscle tumor, and venous leiomyosarcoma (VLMS) is an uncommon subtype, with majority of the cases involving the vena cava. We report a case of a 56-year-old patient initially diagnosed as deep vein thrombosis (DVT) in the common femoral vein who was later diagnosed with primary VLMS originating from the deep femoral vein. Despite anticoagulation therapy, leg edema persisted and imaging studies revealed an intraluminal mass with increased extent and size. Initial duplex ultrasound suggested chronic DVT; however subsequent contrast-enhanced computed tomography and magnetic resonance imaging performed during follow-up demonstrated interval growth of an intraluminal mass, and positron emission tomography-computed tomography later confirmed metabolically active disease, leading to the diagnosis of VLMS. Surgical resection of the mass was performed, followed by reconstruction of the femoral vein using an expanded polytetrafluoroethylene graft. Histopathologic examination confirmed the diagnosis of LMS. The patient had an uneventful postoperative recovery and was referred for adjuvant therapy, including chemotherapy and radiotherapy. This case highlights the importance of a multimodal diagnostic approach in differentiating neoplasms from blood clots and underscores the need for a high level of suspicion when DVT presents with atypical features. Early diagnosis and wide surgical excision with the aim of achieving negative margins are essential for successful management of VLMS.