Spurious metastasis on whole body scans in a patient with thyroid carcinoma.

A young woman received 65 mCi 131I for ablation of recurrent functioning thyroid tissue in the thyroid bed after prior ablation. Following this dose, 131I remained localized bilaterally in submandibular salivary tissue for more than 18 days. There was no evidence of metastatic disease in the salivary glands. The persistent 131I retention, another cause of "spurious metastasis", may have occurred because of protein binding of iodide carried out by salivary peroxidase.