Clinical data: a 23-year old woman was referred for an evaluation of signs of hyperthyroidism.

Palpation: no abnormality.

Functional state: euthyroidism with TSH 1.00 mIU/L.

Ultrasonography: revealed a hypoechogenic nodule in the left lobe. The nodule did not display a halo sign. The presence of perinodular blood flow was doubtful.

Cytology: resulted in atypical follicular tumor.

Histopathological diagnosis: microfollicular adenoma.