Thyroid metastasis of clear cell renal carcinoma: Report of a case.

Renal cell carcinoma can recur many years after diagnosis and nephrectomy metastasizing even in uncommon sites, including thyroid gland. Thyroid metastases are extremely rare, the most frequent site of origin are renal tumors. Metastases in thyroid gland appear as painless nodules or masses, "cold" at scintiscan. We report the case of a 67-year-old male patient affected by clear cell renal carcinoma, diagnosed by fine-needle aspiration cytology procedures, and treated with anticancer medical therapy, who noticed after some months a mass in the neck-thyroid region requiring deeper medical investigations. By this way, thyroid fine-needle aspiration cytology reported a lesion made of malignant epithelial cells compatible with metastases of renal carcinoma (clear cell). Clinical and pathological data, together with immunostaining, supported the diagnosis of metastatic clear cell renal carcinoma. The diagnosis of metastatic disease, although difficult clinically and pathologically, should be suspected in patients with a clinical history of cancer, particularly in case of renal cell carcinoma, but fine-needle aspiration cytology can provide the clue for diagnosis.