The clinial presentation, imaging features and location in the calf are consistent with fibroadipose vascular anomaly, also known as FAVA. The lesions are characterized by deep muscle replacement with fibrofatty overgrowth and phlebectasia (dilation of the veins). Extrafascial components consist of fatty overgrowth, phlebectasia, and an occasional lymphatic malformation. The posterior compartment of the calf is by far the most common location, followed by the wrist and thigh.

The histopathologic features of FAVA are dense fibrous tissue, fat, and lymphoplasmacytic aggregates within atrophied skeletal muscle. Histology also demonstrates large, irregular, and sometimes excessively muscularized venous channels and smaller, clustered channels. Other findings seen include organizing thrombi, a lymphatic component, and dense fibrous tissue-encircled nerves.

Surgical resection is the mainstay of treatment.