[Metastasis of renal carcinoma to the thyroid gland]

Renal clear cell carcinoma (RCCC) is the most common type of kidney cancer, represents 90% of all renal tumors and approximately 3% of all malignant tumors in adulthood, which has unpredictable behavior. It has a peak incidence between the sixth and eighth decades of the life. Distant metastases are frequently found, these may occur decades after the diagnosis. We present a 81-year-old man with a history of RCCC managed with nephrectomy. After 4 years of follow up, he noticed a mass over the thyroid region. Ultrasonography reported a thyroid nodule. Due to the oncologic history, a total thyroidectomy was performed and the microscopic observation revealed polygonal cells with clear cytoplasm, and a fine capillary network around tumor nets. The tumor immunohistochemistry profile confirmed a metastatic RCCC, as tumor cells disclosed strong immunoreaction to RCC, CD10 and PAX-8, and negative for CK7 and TTF-1. This case emphasizes the importance of considering a metastatic origin when finding a thyroid nodule in a patient with a previous history of RCCC.