A 32-YEAR-OLD previously healthy woman was seen for a slowly enlarging right anterior cervical mass. She denied a history of irradiation of the thymus in childhood, previous disease of the thyroid, any familial endocrine syndrome, or any systemic symptoms. Findings from physical examination demonstrated a firm nontender nodule that moved with swallowing and was adherent to the lateral aspect of the right lobe of the thyroid gland. Ultrasonography of the thyroid gland confirmed the presence of a 3.7 × 2.6 × 2.6-cm solid right thyroid nodule. A fine-needle aspiration (FNA) of the nodule was performed and was diagnosed by a cytopathologist as benign thyroid tissue. Levels from thyroid function tests included T4, 172 nmol/L (13.4 µg/dL); T3, 3.90 nmol/L; thyroid-stimulating hormone (TSH), 0.5 mIU/L; T3 resin uptake, 31%; and free thyroxine index, 54 pmol/L (4.2 ng/dL). A thyroid radionuclide scan with 123 I demonstrated a "hot" nodule in the right lobe of the thyroid gland with suppression of all remaining thyroid tissue (Figure 1).