Metastatic thyroid follicular carcinoma presenting as a primary renal tumor.

Renal tumor metastasis from thyroid follicular carcinoma is very rare. Here, we present a 64-year-old woman with metastatic thyroid follicular carcinoma presenting as a primary renal tumor. The renal tumor was removed and revealed the origin of thyroid follicular carcinoma. Six months after the treatment of renal tumor, the patient was readmitted for the enlarged thyroid gland. The follicular carcinoma was revealed in the resected thyroid gland. The serum thyroglobulin level and thyroid function tests were consistently normal. Although with metastasis to the kidney, thyroid follicular carcinoma is thought to have a good prognosis.