Aneurysmal Bone Cyst of the Distal Phalanx: A Case Report.

Aneurysmal bone cysts (ABCs) are rare benign bone lesions, infrequently affecting the hand and exceptionally rare in the distal phalanx. Here, we present a unique case involving a woman aged 33 years who presented with progressive swelling and erythema of the distal phalanx of the right index finger. Magnetic resonance imaging demonstrated features suggestive of ABC, whereas plain radiographs were inconclusive. The patient underwent surgical excision and curettage through a volar approach, preserving the phalanx. Histopathologic examination confirmed the diagnosis, and no adjuvant therapy was administered. At the 4-year follow-up, the patient exhibited a full range of motion, no pain, and no signs of recurrence. To our knowledge, this is the first reported case of distal phalanx ABC in a finger treated with phalanx preservation rather than amputation. This case highlights the importance of including ABC in the differential diagnosis of hand tumors and supports the potential for conservative surgical management.