Abstract
INTRODUCTION: Tenosynovial giant cell tumor (TSGCT), formerly known as pigmented villonodular synovitis, is a rare, benign, locally aggressive neoplasm originating from the tendon, bursa, or synovium. It is broadly categorized into localized TSGCT (L-TSGCT) and diffuse TSGCT types, with the localized form more commonly affecting the tendon sheaths of the hand and fingers. This report describes a rare presentation of a L-TSGCT involving the flexor tendon sheath of the right thumb in a 40-year-old male, managed successfully with complete excision. CASE REPORT: We report a case of a 40-year-old male who presented with a 1-year-old history of a slowly growing, painless mass over the right thumb, along with restriction of movement. Clinical examination revealed a firm, non-tender, mobile mass measuring approximately 3 cm × 3 cm. X-ray revealed a soft-tissue shadow with pressure scalloping and erosion over the distal phalanx of the right thumb. Magnetic resonance imaging (MRI) demonstrated a well-defined lobulated T1 and T2 isointense lesion with erosion of the distal phalanx of the thumb. The patient underwent complete marginal surgical excision along with the use of local adjuvant chemical cauterization of the bony erosion bed with 88% phenol for 1 min to prevent recurrence. Intraoperatively, it was a well-encapsulated, yellowish-brown nodular mass adherent to the flexor sheath without infiltration into the neurovascular bundle. The post-operative course was uneventful, and the patient achieved a full range of motion at 4 months of follow-up. CONCLUSION: L-TSGCT of the thumb is uncommon but should be considered in the differential diagnosis of soft-tissue swellings in the digits. MRI assists in delineating lesion extent and planning surgical excision. Histopathological analysis confirms the diagnosis of L-TSGCT. The tumor's characteristic imaging profile and indolent clinical course highlight the need for accurate pre-operative diagnosis. Complete surgical excision, preferably preserving digital function, remains the gold standard, offering a high chance of cure. Use of adjuvants such as phenol might reduce the risk of recurrences, especially in cases of bony involvement. Long-term follow-up is strictly advisable.