Clinical data: a 60-year-old woman was referred for an evaluation of a rapidly increasing tumor which evolved over 6 weeks.

Palpation: a very hard, fixed tumor in the right lobe and in the isthmic part of the thyroid.

Functional state: euthyroidism (TSH 0.96 mIU/L, FT4 16.6 pM/L).

Ultrasonography: a hypoechogenic mass in the right lobe and in the isthmus with small cystic areas. No vascularization on Doppler mode.

Cytological diagnosis: anaplastic carcinoma.

Histopathology: anaplastic cancer.