First examination (1st and 2nd rows of images):

Clinical presentation: A 60-year-old hypothyroid patient was referred for evaluation of a thyroid nodule.

Palpation: The thyroid was moderately firm, a hard lesion was suspected in the left lobe.

Hormonal investigation indicated euthyroidism on daily 125 microgram levothyroxine with TSH-level 0.81 mIU/L.

Ultrasonography: The thyroid was moderately hypoechogenic with fibrotic changes. There was a hypoechogenic lesion with microcalcification in the left thyroid.

Cytological diagnosis: Hashimoto's thyroiditis.

Follow-up examination 2 years later (3rd and 4th rows of images):

Clinical presentation: The patient visited another clinic for follow-up examination. She was told harboring a suspicious nodule and aspiration cytology resulted in suspicion of carcinoma not otherwise specified.

Palpation: A firm nodule was palpable in the left lobe.

Functional state: euthyroidism on daily 125 microgram levothyroxine (TSH 2.06 mIU/L).

Ultrasonography. The sonographic pattern remained unchanged. The thyroid lobes were hypoechogenic and presented fibrotic changes. There was a more hypoechogenic and less inhomogeneous nodule in the ventral part of the left lobe. The presence of a halo was doubtful as was perilesional vascularity. There were several other, smaller hypoechogenic discrete lesions in both lobes.

Cytological diagnosis: Hashimoto's thyroiditis and suspicion of an oxyphilic tumor with less than 5% estimated risk for carcinoma.

A left lobectomy was performed. Intraoperative frozen section diagnosis indicated a benign lesion.

Histopathology disclosed benign hyperplastic nodules and Hashimoto's thyroiditis.

Comments.

1. Note that the echo structure of the lesion and the extralesional parts of the thyroid are similar. The lesion is presumably a secondary lobule. Nevertheless, the presence of microcalcifications requires a cytological evaluation.

2. It would be very difficult to revise the cytological diagnosis: although there are obvious signs of Hashimoto's thyroiditis, an oxyphilic tumor cannot be excluded.