Clinical presentation: a 33-year-old woman was referred for an evaluation of hyperthyroidism. The patient had typical complaints for 3 weeks, including weight loss, irritability and increased heart rate.

Palpation: no abnormality.

Functional state: moderate degree of hyperthyroidism with TSH 0.01 mIU/L, FT4 46.3 pM/L.

Ultrasonography: around 60% of the thyroids were markedly hypoechogenic. There were no lesions fitting a nodule. The vascularization was a little bit increased.

FNAC: disclosed Hashimoto's thyroiditis.

We performed TsAb test which gave negative result.

Beta-blocking agent was administered, 6 weeks later the hyperthyroidism has spontaneously resolved (FT4 10.7 pM/L), another 12 weeks later hypothyroidism has developed (TSH 11.9 mIU/L, FT4 9.73 pM/L), which has worsened 1 year after the initial examination. Replacement therapy was started.

Comment: we think that FNAC may have a role even in non-nodular thyroid disorders. In this case we could give a final diagnosis within 20 minutes. Therefore both a second visit and a delay in the correct therapy could be avoided. The performance of FNAC in such cases may have further professional advantages. TsAB assay has its own limitations with a less than 90% sensitivity.