This is a path-proven alveolar soft part sarcoma of the right lower extremity, with metastases to the brain and lungs at diagnosis. The patient underwent above knee amputation and did well post-operatively.
Alveolar soft part sarcoma is a very rare, highly vascular, deep soft tissue malignancy that is classically seen in young adults, with a slight female predilection. It accounts for <1% of all soft-tissue sarcomas. It most frequently arises from the lower extremities. Distant metastases at the time of diagnosis is a relatively common feature, with metastases often spreading to the lungs, bone and brain.
On MRI, alveolar soft part sarcoma often presents as a large, highly vascular mass that is T1 isointense or slightly hyperintense and T2 hyperintense, with heterogeneous contrast enhancement. Associated vascular signal voids are common secondary to large peritumoral blood vessels.