Thyroid abnormality secondary to tortuous carotid artery.

A 59-year-old man was referred to the nuclear medicine service for a thyroid scan, as his neck was thick and the thyroid was not palpable. In the past the patient had undergone head and neck irradiation for acne. A 123I-thyroid scan was interpreted as a "cold" nodule in the lower pole of the right lobe, but thyroid ultrasound showed no thyroid abnormality. Repeat ultrasound examination eventually showed a tortuous carotid artery behind the lower pole of the right lobe of the thyroid that corresponded to the "cold" defect.