A case of solitary metastasis of renal cell carcinoma to the thyroid gland is presented. The patient was a 82-year-old man found to have an abnormal mass in his neck. He had a past history of renal clear cell carcinoma of the left kidney (pT1aN0M0, G12, alveolar type, clear cell subtype), which had been resected 12 years previously. Ultrasonography revealed a tumor mass in the right hemithyroid gland. This time fine needle biopsy of the thyroid tumor suggested metastatic thyroid carcinoma. Right hemithyroidectomy was performed last year. The histopathological findings were suggestive of clear cell carcinoma, thus metastatic renal carcinoma was diagnosed. This is the 26th case of thyroid solitary metastasis of clear cell renal cell carcinoma reported in Japan to date.
