Thyroid metastases from a ductal carcinoma of the breast. A case report.

A case of bilateral thyroid metastases from ductal carcinoma of the breast is presented with emphasis on some unusual clinical findings: presentation after a long disease-free interval; clinical signs mimicking an acute thyroiditis; cystic structure of the left-sided metastatic nodule. Fine needle aspiration cytology from both nodules showed highly atypical tumor cells, such as to warrant a differential diagnosis between metastatic breast cancer on the one hand and anaplastic and medullary carcinoma of the thyroid on the other. Immunophenotypic study of the neoplasm on a cell block preparation of the aspirated material showed negativity for both thyroglobulin and calcitonin; instead, the tumor cells were strongly stained with antibodies against the "breast-related" markers alpha-lactalbumin and gross cystic disease fluid protein-15. Therefore, immunochemistry allowed us to establish a definite diagnosis of metastatic breast disease of the thyroid, thereby avoiding surgical procedures.