Metastasis from renal cell carcinoma to thyroid presenting as rapidly growing neck mass

INTRODUCTION: Renal cell carcinoma (RCC) is commonly known as the “internist's tumor” because of its unpredictable behavior. Metastasis to the thyroid gland is rarely found in clinical practice. PRESENTATION OF CASE: We report a rare case of non-thyroid malignancies NTM from renal cell carcinoma 1.5 years after radical nephrectomy in a 58-year-old man with a rapidly growing neck mass. DISCUSSION: Malignant melanoma, breast carcinoma, lung, and skin cancer are the most common sources of non-thyroid malignancies (NTM). Although metastases of NTMs to the thyroid gland are uncommon in clinical practice, it should be considered in patients with a history of prior malignancy and a new thyroid mass. CONCLUSION: Isolated thyroid metastasis should be considered in patients with a previous history of cancer and newly developing thyroid mass.