Clinical data: A 40-year-old woman was referred for evaluation of a newly diagnosed thyroid nodule. She had been treated for hypothyroidism for 4 years.

Palpation: Both lobes were firm. No nodule could be palpated.

Laboratory tests: TSH 1.79 mIU/L on daily 175 microgram levothyroxine.

Ultrasound. The thyroid was composed of moderately and minimally hypoechoic areas. There were several discrete lesions within. The largest of them in the upper pole of the left lobe was probably a nodule. This had halo and perinodular blood flow.

Aspiration cytology from the hyperechogenic lesion resulted in Hashimoto's thyroiditis.