The thyroid gland is one of the most vascularized organs in the body. However, metastatic disease to the thyroid gland is rare. When it does occur kidney is the most common primary tumor site, followed by melanoma, lung, breast, esophagus, uterus and colon carcinoma. We describe the case of an isolated thyroid metastasis from clear cell renal carcinoma occurring 16 years after nephrectomy. An 82 years-old woman presented for the recent growth of a right thyroid nodule, diagnosed 3 years before, when a fine needle aspiration biopsy found a benign cytology suggesting a well-differentiated follicular thyroid adenoma. Her medical history included type 2 diabetes mellitus, atrial fibrillation and a right nephrectomy for a clear cell renal carcinoma done 16 years before. The patient has lost weight but she was otherwise asymptomatic. The right lobe goiter was painless, firm, and mobile with deglutition, without signs of local compression or latero-cervical lymphadenopathy. Thyroid ultrasonography revealed an enlarged (9.9 cm) macronodular right lobe, with multiple cystic areas, with normal left lobe and a thrombus in the right internal jugular vein. Thyroid function tests were normal. The patient was suspected of thyroid carcinoma and underwent a near total thyroidectomy. Histopathological examination revealed a metastasis of clear cell renal carcinoma in the right thyroid gland lobe (8.5/5/5 cm). Further imaging showed no primary tumor or other metastases. Metastatic renal carcinoma to the thyroid should be considered in any patient presenting with a thyroid mass and a medical history of operated renal cell carcinoma, since it can occur up to 25 years after nephrectomy.
Keywords: clear cell renal carcinoma; metastasis; thyroid secondary neoplasm.