Clinical data: a 77-year-old woman was referred for an examination because of a tumor which evolved over three weeks. The patient had palsy of the left recurrent nerve.

Palpation: a large, stone-hard tumor in the left thyroid.

Functional state: subclinical hyperthyroidism (TSH 0.03 mIU/L, FT4 12.1 pM/L, FT3 4.96 pM/L).

Ultrasonography: the right thyroid was intact. The left lobe was extremely enlarged with the dimensions of 55x50x180 mm. It was composed of multiple hypoechogenic nodules which contained echonormal areas and cystic lesions. One of them is demonstrated on the ultrasonographic images.

Cytological diagnosis: anaplastic carcinoma.

Histopathology: anaplastic cancer.