Metastases from renal cell cancer to the thyroid gland. a systematic review of 175 cases between 1964 and 2016

Abstract – Background: Renal Cell Cancer (RCC) is the most common extra-thyroid cancer metastasizing to the thyroid gland and has been responsible for 48.1% metastases of Non-Thyroid Malignancies (NTMs) to the thyroid in the past decade. Metastases to the thyroid gland have been reported in 1.4%-3% of patients undergoing thyroid surgery for thyroid malignancies. We systematically reviewed the literature from 1964 to 2016 and herein present our experience. Patients and Methods: The research was systematically performed on Pubmed, EMbase and Cochrane Library databases by entering the strings: “renal carcinoma AND thyroid metastasis” or “renal carcinoma AND thyroid metastases” or “hypernephroma AND thyroid metastasis (or metastases)”. Results: 175 cases were retrieved and 90 were included in the study since they fulfilled the inclusion criteria by reporting gender, age, latency of metastases presentation after nephrectomy, jugular vein infiltration and other sites of metastasis (when applicable). The mean age of thyroid metastases presentation is 64.4 years and the mean latency after a nephrectomy is 9.1 years (range 0-24). Fine needle aspiration biopsy (FNAB) failed to provide the correct diagnosis in 28.7% of patients with thyroid metastases from RCC. Conclusions: Given the long latency, RCC follow-up program should be longer than recommended at present and implemented with an ultrasound scan of the neck.