Clinical data: a 61-year-old woman was referred for an evaluation of a rapidly growing mass in the right thyroid. The tumor had evolved over 5 weeks.

Palpation: a very hard, not freely moveable nodule in the moderately enlarged right lobe. Multiple nodules were palpable in both lobes.

Functional state: euthyroidism (TSH-level 0.48 mIU/L).

Ultrasonography: the basic echo structure of the thyroid was normal. There were multiple hypoechogenic nodules in the right lobe.

Cytological picture: there is no colloid in the background. Thyrocytes occur mostly dissociated. Great proportion of follicular cells exhibit oxyphilic metaplasia. The nuclei present moderate degree of anisonucleosis and several cells contain intranuclear inclusions. Otherwise, the cytological pattern is identical with that observed in a Hürthle-cell tumor. Cytological diagnosis: oxyphilic tumor with higher than the average risk for invasive tumor.

Combined clinical-cytological diagnosis: thyroid cancer, possible anaplastic cancer.

Histopathology: anaplastic cancer.

Comment: this is an unusual cytological pattern bacause of the relatively reassuring pattern and the lack of pleomorphic cells on the smears. The cytological pattern is in sharp contrast with the clinical picture.