Unusual Presentation of Tenosynovial Giant Cell Tumor in an Unusual Location – Hypothenar Region

Tenosynovial giant cell tumors (TGCTs) are tumors of the tendon sheath and are usually seen proximal to the wrist joint or in fingers, contrary to this case, as seen in the hypothenar region. It is primarily caused by a mutation in the synovial membrane’s stromal cells, which results in an overexpression of colony-stimulating factor. A 34-year-old male presented with swelling over the right hand palmar aspect over the hypothenar eminence which was gradually progressive in nature. The site and local examination of swelling seemed to have pertaining with TGCT, fibroma of tendinous sheath, cyst, rheumatoid nodule, or neuroma. Radiological tests were performed, and contrast magnetic resonance imaging image showed soft tissue density peri-articular mass. Fine-needle aspiration cytology was performed which confirmed the diagnosis as giant cell tumor of the tendon sheath/TGCT. Excision biopsy was performed. This case is an unusual presentation of TGCT in an unusual location, which turned into a diagnostic dilemma on clinical and radiological assessment. It was only after the gold standard histopathological report that the diagnosis of TGCT was reached and confirmed, followed by appropriate management.