Calcifying Aponeurotic Fibroma in the Deep Space of the Hand.

Calcifying aponeurotic fibroma is a rare tumor that can involve the upper extremity, but deep hand space involvement is exceptionally uncommon and presents unique diagnostic and treatment challenges. We present a 9-year-old girl with a progressively enlarging mass on the ulnar side of the left palm. Magnetic resonance imaging revealed an ill-defined tumor with fatty infiltration spanning the third and fourth metacarpal spaces, suspicious of an aggressive tumor. The delay in diagnosis, likely stemming from the location in the deep space of the palm and lack of functional impairment, allowed this lesion to become atypically large and expansive. Given the child's age, a marginal excision was performed with careful preservation of the adjacent tendons, bone, and neurovascular structures. Although long-term monitoring for recurrence is ongoing, the patient had no evidence of recurrence at 1-year follow-up.