Clinical presentation: A 51-year-old woman was referred for FNAC of a suspected metastasis of a breast cancer to the thyroid. She has been operated for ductal invasive breast cancer on the left 6 months earlier. Ultrasonography of the thyroid revealed a multinodular goiter.

Palpation: the presence of a nodule in the right lobe was questionable.

Functional state: euthyroidism.

Ultrasonography. There were two hypoechogenic nodules in the right lobe.

Cytological diagnosis: malignancy, i.e., a cytological picture corresponding to a metastatic breast cancer.

Thyroglobulin immunocytochemistry: negative result.

Further evaluation of the patient revealed metastasis in the lung and in the liver.

Comment. The knowledge of the clinical history was essential because in most cases a reliable cytological distinction between a metastatic breast cancer and a papillary or oxyphilic cell carcinoma of the thyroid is not possible.