Clinical presentation: a 47-year-old woman requested a second opinion. He was treated for hyperthyroidism for a month when ultrasonography and FNAC were performed. The latter resulted in atypia of unknown significance.

Palpation: both thyroids were enlarged and moderately firm.

Results of blood tests: euthyroidism on daily 15 mg methimazole (TSH 1.74 mIU/L, FT4 16.7 pM/L).

Ultrasonography: a diffusely hypoechogenic thyroid was found with moderate degree of fibrosis. There was an echonormal nodule in the lower pole of the left lobe. The nodule presented an incomplete halo sign while the presence of perinodular blood flow was equivocal.

Cytology: was performed from the hyperechogenic nodule.

Cytological diagnosis: papillary cancer cannot be excluded. Considering the sonographic, clinical and cytological data the risk of malignancy was estimated as 20%.

Surgery was performed.

Histopathology: diffuse goiter corresponding to Graves disease. Benign hyperplastic nodular goiter in the left lobe.

Comments:

1. This case history reveals the problem with category AUS of Bethesda reporting system. Why do we think that an atypia of unknown significance will disappear over time? And if we do not find atypical cells on a repeat aspiration why don`t we  have to consider the possibility of failure of the aspiration of a small tumor at the second occasion?

2. The fibrotic change may be misinterpreted as microcalcification - see comment to ultrasonographic picture 2.

3. Another possible failure, the misinterpretation of the increased extranodular vascularization as perinodular blood flow is demonstrated on ultrasonographic picture 8 and 9.

4. The cytological presentation is also very edifying. The presence of inclusions and grooves and that of multinucleated giant cell raised the possibility of a papillary cancer.

5. The judgement of the basic echostructure of a nodule is difficult in the event of a hypoechogenic thyroid. While the risk of malignancy is negligible in echonormal nodules in a non-autoimmune, i.e. echonormal thyroid, this possibility is greater in an echonormal nodule presented in an autoimmune thyroid disease.