A case of intra-articular angioleiomyoma of the talocrural joint.

Angioleiomyoma is a benign pericytic neoplasm with smooth muscle differentiation. Intra-articular angioleiomyoma is exceptionally rare with only four cases reported, all involving the knee joint. Here we report the first case of intra-articular angioleiomyoma entirely localized within the ankle joint. An 83-year-old male presented with progressively worsening ankle pain. Subsequent magnetic resonance imaging showed a soft tissue mass within the talocrural joint. Histologic examination and ancillary testing demonstrated fascicles of smooth muscle cells and interspersed, often compressed, vascular channels, consistent with an angioleiomyoma. This case highlights the importance of including angioleiomyoma in the differential diagnosis of an ankle joint mass.