Chondroblastoma of Metacarpal Masquerading as Enchondroma - A Case Report.

Introduction: Chondroblastoma is a rare and benign bone neoplasm that accounts for <1% of all bone tumors. Chondroblastomas of the hand are extremely rare, while enchondromas are the most common bone tumor of the hand. Case Report: A 14-year-old girl had complaints of pain and swelling over the base of her thumb for 1 year. On examination, a solitary and hard swelling was palpable over the base of the thumb, with terminal restriction of first metacarpophalangeal joint movements. Radiographs revealed an expansile and lytic lesion in the epiphyseal region of the first metacarpal. Chondroid calcifications were absent. Magnetic resonance imaging showed a lesion with the hypointense signal on T1 and T2 sequences. These suggested a diagnosis of enchondroma. Excisional biopsy of the lesion, bone grafting, and Kirschner wire fixation was performed. Histological examination showed the lesion to be a chondroblastoma. No recurrence was noted at the 1-year follow-up. Conclusion: Chondroblastomas can very rarely occur in the bones of the hand. In such cases, differentiating them from enchondromas and ABCs is a challenge. Characteristic chondroid calcifications may be absent in nearly half of such cases. Curettage with bone grafting provides a good outcome with no recurrence.