RESUMO
Giant cell tumour of tendon sheath is an uncommon benign soft tissue tumour. Histopathological examination plays a crucial role in the definitive diagnosis of giant cell tumour although pre-operative imaging supports its suspicion. We report a case of a giant cell tumour of the tendon sheath in a 26-year-old man as a painless, firm, localized, slow-growing benign soft tissue tumour of the thumb; managed by complete excision. The patient continues to do well at 7 months post-surgery with no complaints and no signs of recurrence. Giant cell tumour of the phalanges is a locally aggressive entity; therefore delayed or missed diagnosis of giant cell tumour especially of the thumb distal phalanx can be extremely debilitating. Hence, high degree of suspicion and early en bloc resection is the key to its management. Keywords: case reports; giant cell tumors; tendons; thumb.