Thyroid metastasis from renal cell carcinoma—A case report after 9 years

• The thyroid gland is a rare site of clinically detectable tumor metastasis.
• Preoperative distinction between primary and secondary thyroid tumors is difficult.
• RCC disseminates in an unpredictable manner and can show late recurrences.
• Metastasis should be considered if history for RCC and a thyroid nodule is present.

IntroductionThe thyroid gland is a rare site of clinically detectable tumor metastasis. As thyroid tumors are usually assumed to be primary in origin, its recognition as a secondary is difficult.Presentation of caseWe report a case of an 80-year old female who was referred to the Department of Surgery for a symptomatic thyroid nodule. Her medical history included a radical nephrectomy for renal cell carcinoma (RCC) nine years ago. During follow-up a pancreatic nodule was noted suggestive of a neuroendocrine tumor and the von Hippel-Lindau syndrome had to be ruled out. The fine-needle aspiration biopsy (FNAB) guided by ultrasound (US) of the thyroid nodule was inconclusive and a hemithyroidectomy and isthmectomy were performed. Histological examination revealed metastasis of a clear cell carcinoma.DiscussionRCC disseminates in an unpredictable manner and can show late recurrences. Although secondary involvement of the thyroid gland by RCC is rare, it is still one of the more common neoplasms to metastasize to this site. There are no specific clinical features and few characteristic findings of metastatic thyroid carcinoma on imaging studies. FNAB is a useful procedure to diagnose metastatic thyroid cancer, but one should remain suspicious when the result for malignant cells is negative or indeterminate. After thyroidectomy the diagnosis of RCC is confirmed immunohistochemically. There is a clear survival benefit if a surgical approach to the thyroid metastasis is chosen.ConclusionThyroid metastasis should be considered in patients with a thyroid nodule and positive history for RCC.