Multicentric Calcifying Aponeurotic Fibroma of the Upper Extremity With Associated Nerve Compression and Bony Dysplasia.

A 19-year-old woman with presumed history of lymphatic malformation of her right elbow and wrist with intermittent mild pain, positive Tinel sign at the proximal forearm, elbow contracture, and limited pronosupination presented for a second opinion. She had been diagnosed clinically with a vascular malformation in infancy with subsequent magnetic resonance imaging findings of a fatty tumor versus malformation. She was treated conservatively with splinting for her range of motion limitations for years. Ultimately, magnetic resonance-guided biopsy demonstrated calcifying aponeurotic fibroma (CAF). Computed tomography and magnetic resonance imaging further demonstrated a dysplastic distal radioulnar joint and fatty muscle atrophy at the proximal forearm. Excisional biopsy of the two lesions demonstrated multicentric CAF. Multicentric CAF is exceedingly rare as are associated nerve compression and bony dysplasia. This case adds to our collective knowledge on CAF to better elucidate the pathogenesis as well as bring greater awareness of this rare tumor to aid practitioners in avoiding misdiagnoses as in our patient.