Radioiodine uptake in the head and neck

To report two cases of sinusitis-associated radioiodine uptake in patients with thyroid cancer and to review the reported causes of false-positive radioiodine uptake in the head and neck area.

We present the radiologic findings in two patients who had undergone treatment for papillary thyroid cancer and discuss other settings in which radioiodine uptake suggested the presence of metastatic disease.

Radioiodine whole-body scans of two patients who had had thyroid cancer demonstrated uptake in the sphenoid and maxillary sinuses, respectively, mimicking bone or brain metastatic involvement. The thyroglobulin levels were low. Computed tomographic (CT) scanning disclosed mucosal swelling in the sinuses, consistent with sinusitis. The radioiodine uptake cleared on a follow-up scan in one case and was more localized than the CT findings in the other. Eighteen causes of false-positive radioiodine uptake in the head and neck area have been reported. On the basis of the mechanism of uptake, they can be classified into four categories: (1) physiologic uptake (ectopic thyroid tissue), (2) nonthyroidal pathologic conditions (dacryocystitis, sinusitis, sinus mucocele, sialadenitis, folliculitis, Warthin's tumor, parotid cyst, porencephaly, posttraumatic cerebromalacia, and inflammation due to dental disease or a nose ring), (3) internal retention (ectasia of the carotid artery and an artificial eye), and (4) external contamination by body secretions (sweat and nasal, tracheobronchial, lacrimal, and salivary secretions). The estimated prevalence of external contamination in the head and neck area on whole-body radioiodine scans is 0.3%.

Physicians should rule out the presence of radioiodine uptake by inflamed mucosa of the paranasal sinuses, as well as various other causes of false-positive radioiodine uptake, before metastatic thyroid cancer in the head and neck area is diagnosed.