Clinical data: A 38-year-old woman was referred for aspiration cytology. She has been treated for hypothyroidism for six months.

Palpation: no abnormality.

Functional state: euthyroidism on daily 75 microgram levothyroxine (TSH 2.97 mIU/L).

Ultrasonography. The thyroid was minimally hypoechogenic. The left lobe contained a cystic lesion that was completely or almost completely cystic. The lobe had two hypoechogenic nodules next to each other, which presented microcalcifications and irregularly increased intranodular vascularization.

Cytology resulted in the suspicion of oxyphilic variant of papillary carcinoma.

A total thyroidectomy was performed. Histopathology disclosed Hashimoto's thyroiditis. The cystic lesion proved to be a hyperplastic nodule while corresponding to the nodules in the lower part of the left lobe, oxyphilic variant of papillary carcinoma was diagnosed.

Comment.

1. Histopathology disclosed a T1 tumor without any extrathyroidal extension. Except for the ventral part of the lower lesion, the tumor was covered by normal parenchyma. The tumor was abutting the capsule of the thyroid by more than 25%. The capsule was continuous.

2. It was doubtful whether the cystic lesion was true nodule or a normal finding, a dilated marcofollicle. The histopathologist did not find any lesion corresponding to the cystic lesion, so it was only a cystic area and not a pathological nodule.