Clinical presentation: A 26-year-old man requested a repeat examination. Ha was discovered having a thyroid nodule 18 months ago when we aspirated 9 mL brown fluid form a nodule located in the isthmus. The cytology resulted in benign lesion. A few weeks before the present examination, the patient noticed a sudden increase in the size of the nodule which caused neck discomfort.

Palpation: There was an elastic nodule in the isthmus while a not firm nodule in the lower part of the left lobe.

Laboratory test: TSH 2.08 mIU/L, FT4 13.6 pM/L, aTPO 8 U/mL.

Ultrasonography. The right lobe was echonormal and had several hypoechogenic tiny areas. There were two cystic nodules, one in the isthmus having a hypoechogenic solid part containing echonormal area and another nodule in the lower pole of the left lobe presenting an echonormal solid area. After removing 8 mL cystic fluid form the nodule in the isthmus, an irregularly shaped hypoechogenic lesion was found having an echonormal area.

Cytology. The smear prepared from the cystic fluid contained only macrophages while the smear of the solid part contained oxyphilic cells and relatively small number of lymphocytes, the latter could be detected even mixed with oxyphilic cell groups.

Combined ultrasound-cytological diagnosis resulted in benign oxyphilic degeneration.

The patient decided to undergo surgery. The isthmus and the left lobe were removed. Histopathology disclosed nodular Hashimoto's thyroiditis in the isthmus and the left lobe.

Comments.

1. It is worth analyzing the solid part of the nodule in the isthmus which has one of the most typical presentation of Hashimoto's thyroiditis: a hypoechogenic lesion having echonormal areas. Nevertheless, there are no ultrasound signs in the extranodular tissue which raise the possibility of thyroiditis.

2. By taking the ultrasound pattern into account we could avoid the overinterpretation of the cytological smear: the possibility of the oxyphilic variant of a papillary carcinoma could be excluded on cytology while the lack of halo sign and perinodular blood flow are very strong features against a follicular-type tumor.