Unusual Uptake of [(131)I] in a Tenosynovial Giant Cell Tumour Relapse in a Patient with Differentiated Thyroid Cancer

A 77-year-old woman with follicular thyroid cancer underwent total thyroidectomy and subsequent Iodine-131 remnant ablation. She had a history of a wide tenosynovial giant cell tumor (TGCT) of the right wrist and hand that had been resected thirteen years ago. Post-therapeutic scintigraphy and single photon emission computed tomography showed mild uptake on the distal right forearm, wrist and hand. Magnetic resonance imaging and posterior histopathology confirmed a relapse of TGCT. No radioiodine adverse effects were reported after a one-year follow-up. As far as we know, this report is the first in the literature to a TGCT visualized on post-therapy radioiodine scan.