Clinical data: a 75-year-old woman was referred for an evaluation of a progressive thyroid enlargement. The patient was operated on benign nodular goiter 50 years earlier. She told that her thyroid was enlarged just after the operation but caused no complaints. She noticed a sudden increase in the last two months, which caused dyspnea and dysphagia.

Palpation: a very hard, almost fixed left thyroid.

Functional state: subclinical hyperthyroidism (TSH 0.09 mIU/L, FT4 15.7 pM/L, FT3 4.66 pM/L).

Ultrasonography: an extremely enlarged left thyroid which was composed of multiple hypoechogenic nodules. The dimensions of the left lobe were 150x180x350 mm.

Cytological report: anaplastic cancer.

Histopathology: anaplastic cancer.