A 42-year-old man had a 4 cm × 4 cm painless ulcer over the right medial malleolus for 6 months. He has a history of deep vein thrombosis that occurred during a femur fracture 30 years ago. Pedal pulses are palpable. There is 2+ edema of the right lower extremity. Left lower extremity is normal. Most likely cause of the ulcer?
A) Venous insufficiency
B) Arterial insufficiency
C) Diabetic neuropathic ulcer
D) Ecthyma gangrenosum