A 56-year-old female patient presented with a swollen and painful right ankle. She reported a trauma to this ankle twenty years ago. She had noticed a growing soft-tissue mass on the right ankle for the past four years. The mass was associated with swelling and pain that became aggravated while walking. In the past two years, surgical excision had been performed twice to remove the mass due to its recurrence and accompanying severe pain. The histological result was not available at admission. A Dual Energy CT (DECT) examination was requested for further evaluation.