Renal metastasis from thyroid carcinoma 35 years after detection of the primary tumor.

A case of a solitary, unilateral, large metastatic renal tumor found 35 years after the detection of primary thyroid carcinoma is presented. Renal metastasis from thyroid carcinoma detected during life is extremely rare, and there may be a long latency period before the appearance of a secondary tumor. The possibility of a secondary tumor should always be considered in the differential diagnosis of renal neoplasms, even when the tumor is a large, unilateral, solitary renal mass.