False Positive Findings in F-18 FDG PET and Whole Body Scans With I-131 in Warthin Tumor of the Parotid Gland

A 52-year-old woman underwent total thyroidectomy, bilateral cervical lymphadenectomy, and radioiodine therapy, with 7.9 GBq (213 mCi), iodine-131 for papillary thyroid cancer (T3). Six months later, F-18 FDG PET-CT scans revealed a suspicious lesion of the left parotid gland with focal glucose uptake and increased uptake of iodine-131 on scintigraphy. Thyroglobulin level was about 4 ng/L. After radioiodine therapy with 9.3 GBq (251 mCi) iodine-131, the follow-up scintigraphy still showed a suspicious radioiodine uptake, and the patient was referred for parotidectomy. Here, histopathologic examination revealed a Warthin tumor of the parotid gland. This case shows that increased uptake of iodine-131 in scintigraphy and of glucose in PET can occur in benign parotid gland disease.