Intrathyroid metastasis of breast cancer: Sonographic findings.

Metastasis of ductal carcinoma of the breast to the thyroid gland is uncommon and usually detected at autopsy. The incidences of metastases to the thyroid have been reported at 3%, and the most common primary malignancy is renal cell carcinoma. We report a rare case of intrathyroid metastatsis of breast ductal carcinoma in a patient who was treated for breast cancer 15 years earlier.