Pre-therapy hyperfunctioning follicular thyroid carcinoma evaluation with I-131 whole-body scan and with F-18 FDG PET/CT.

We describe a patient with persistent hyperthyroidism after total thyroidectomy for toxic multinodular goiter and without therapy with levothyroxine evaluated with I-131 whole-body scan and with F-18 FDG PET/CT scan. Scintigraphy performed 48 hours after radiopharmaceutical administration showed many areas of focal radioiodine uptake. A week later we performed a PET/CT scan to better localize the anatomic site of the iodine-positive lesions. Both scans, performed after methimazole withdrawal, visualized the same lesions, and these results were used as a guide for biopsy. Histologic examination was consistent with metastatic follicular thyroid carcinoma.