A case report of giant cell tumor of the extensor tendon sheath in index finger

Giant cell tumor of the tendon sheath (GCTTS) is an uncommon benign soft tissue lesion of uncertain etiology. Although it predominantly involves the hand, occurrences in the ankle and foot have also been reported but remain rare. Patients typically present with a painless, palpable mass that has often been present for an extended duration. While imaging studies and fine-needle aspiration cytology (FNAC) may suggest the diagnosis, definitive confirmation relies on histopathological examination following surgical excision. This report describes a rare case of GCTTS involving the extensor tendon sheath of the right index finger. A 38-year-old male presented with a 4-year history of a gradually enlarging, painless swelling on the dorsal aspect of the right index finger. Clinical examination revealed a well- defined, firm, 4 cm × 1.5 cm mass located over the proximal phalanx. The swelling had a smooth surface, uniform consistency, and was easily mobile in the lateral plane. Radiographic imaging of the hand showed a localized soft tissue shadow without any evidence of bony involvement. Ultrasonography revealed a soft tissue mass, and FNAC was suggestive of GCTTS. The lesion was subsequently excised, and histopathological analysis confirmed the diagnosis by demonstrating characteristic features of GCTTS. Given its indolent course and subtle presentation, GCTTS should be considered in the differential diagnosis of soft tissue swellings in the hand, particularly in adults. FNAC, followed by surgical excision and histopathological evaluation, remains both diagnostic and therapeutic. Ongoing follow-up is recommended due to the potential for local recurrence.