Clinical presentation: a 71-year-old woman with a nodule discovered 6 weeks earlier.

Palpation: the right thyroid was extremely enlarged and hard.

Functional state: euthyroidism with TSH-level 2.71 mIU/L.

Ultrasonography: the right lobe was composed of two hypoechogenic nodules. A similar lesion was found lateral to the right lobe.

Cytological picture: no colloid in the background. Dispersed, mostly naked cells predominate the smear. The pattern resembles a lymphoplasmacytoid population. A few polygonal cells were observed on the smear.

Two possibilities had to be taken into account, a small cell malignant tumor and medullary cancer. We indicated blood test for calcitonin which resulted in 701 pg/mL (normal value: 2-10).

Combined preoperative diagnosis: medullary cancer.

Histopathology: medullary cancer with direct spread outside the thyroid.