Unusual Uptake of [131I] 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 [131I] remnant ablation. She had history of a wide tenosynovial giant cell tumour (TGCT) of the right wrist and hand resected thirteen years ago. Post-therapeutic scintigraphy and SPECT showed mild uptake on distal right forearm, wrist and hand. Magnetic Resonance Imaging and posterior histopathology confirmed relapse of TGCT. No radioiodine adverse effects were reported after one-year follow-up. To the best of our knowledge, this is the first report in the literature of a TGCT visualized on post-therapy radioiodine scan.