Vascular Leiomyosarcoma Masquerading as Chronic Deep Venous Thrombosis

A 78-year-old man with a history of DVT on apixaban presented with bilateral leg pain and dyspnea. Chest CTA ruled out pulmonary embolism but revealed bilateral pulmonary nodules. Biopsy identified a spindle cell neoplasm. 18 F-FDG PET and duplex ultrasound imaging revealed intensely FDG-avid, intraluminal masses in the right femoral and popliteal veins. MRI confirmed lesions with peripheral enhancement. Biopsy of one of the femoral vein masses showed a high-grade spindle cell neoplasm positive for SMSA and desmin, consistent with leiomyosarcoma. This rare vascular tumor mimicked DVT, highlighting the importance of multimodal imaging and biopsy in diagnosing intravascular malignancies with metastatic potential.