Secondary malignancy of the thyroid gland: a case report and review of the literature.

Metastatic cancer to the thyroid gland is uncommon. In this report we describe a patient with a malignant fibrous histiocytoma that metastasized to the thyroid, possibly to a preexisting thyroid nodule. A review of the literature reveals that breast and lung carcinoma are the most frequently identified sources of secondary thyroid carcinoma found at autopsy, while renal carcinoma comprises over 50% of secondary thyroid malignancies discovered clinically. A number of authors suggest that preexisting thyroid disease (i.e., multinodular goiter and thyroid nodules) may provide a nidus for metastases to the thyroid gland.