Thyroid metastasis of clear renal cell carcinoma: a case report and review of the literature.

The thyroid is a rare site for finding tumor metastases. Renal, colorectal, pulmonary, and mammary origin are the most frequent primary neoplasms. Clinical suspicion, early diagnosis, and active surveillance are important during follow-up. Thyroid ultrasound and fine needle aspiration thyroid ultrasound are crucial during follow-up. We present a case of a 66-year-old male who was referred to our Endocrinology and Nutrition Department of the Hospital General Universitario Santa Lucía due to a multinodular goiter. The patient had no symptoms of hyperthyroidism or hypothyroidism. No weight loss or constitutional syndrome was reported. The patient was suffering from a renal clear cell carcinoma with T3aNxM0 stage operated on using a nephrectomy technique in 2012. In a new follow-up, a positron emission tomography-computed tomography (PET-CT) scan was conducted and a multinodular goiter was found with an increase in size and metabolism at the expense of a right thyroid nodule and thyroid ultrasound and fine needle aspiration thyroid ultrasound was requested with the diagnosis of renal cell carcinoma metastasis. We present a rare case report since both metastases (thyroid and pulmonary) could be surgically intervened with curative intent and a review of the literature. This case emphasizes the importance of considering a metastatic origin when finding a thyroid nodule in a patient with a previous history of clear renal cell carcinoma even years after treatment with curative intent.