Breast Metastases to Thyroid Gland

Metastases to the thyroid gland are uncommon. We present the sonographic features of metastatic breast adenocarcinoma to the thyroid in a 67-year-old woman. The lesion measured up to 0.9 cm in diameter, contained an echogenic focus with associated ring-down, and was predominantly cystic, thereby resembling a benign nodule. Because of the patient's history of breast adenocarcinoma, the nodule nevertheless underwent fine-needle aspiration. The unusual appearance of the thyroid nodule underscores the importance of considering patient history in deciding whether obtaining tissue diagnosis of thyroid nodules is warranted.