Clinical presentation: A 39-year-old man was referred for evaluation of a recurrent thyroid cyst which was aspirated 4 months ago. The cyst has recurred within several weeks and caused difficulties in swallowing.

Palpation: an elastic nodule in the left lobe.

Laboratory tests: TSH 3.15 mIU/L, aTPO 0 U/mL.

Ultrasonography. The right lobe was echonormal and contained several minimally hypoechogenic areas. There was a large, cystic nodule in the left lobe with an echonormal solid area in the dorsal part.

50 mL brown fluid was aspirated. Cytology: non-diagnostic report, cystic lesion.

A left lobectomy was performed. Histopathology: benign hyperplastic nodule and chronic lymphocytic thyroiditis.

Comments. There were two conditions suggesting an underlying thyroiditis. First, the echo pattern of the right lobe which showed minimally hypoechogenic areas. Second, the TSH which was in the upper-normal range. None of them proves thyroiditis itself but could raise this possibility. On our experience, the sensitivity of aTPO might be significantly overestimated in the thyroid literature. In such mild forms of thyroiditis, the ultrasound has a better sensitivity.