Metastatic clear cell renal cell carcinoma to the thyroid gland: Case report and a brief review of the literature

Metastatic clear cell renal cell carcinoma (ccRCC) to the thyroid gland is an uncommon but significant presentation, often occurring years after primary tumor resection. We present the case of a 52-year-old female who developed a solitary thyroid metastasis 13 years after undergoing left nephrectomy for ccRCC. Initially presenting with a gradually enlarging neck mass and mild dysphagia, her thyroid nodule exhibited suspicious features on ultrasonography and computed tomography, including hypervascularity. Fine-needle aspiration cytology revealed clear-cell features, prompting a multidisciplinary discussion. Definitive diagnosis was established through right thyroid lobectomy and subsequent immunohistochemical analysis, which confirmed metastatic ccRCC (positive for PAX8, CD10, vimentin; negative for thyroglobulin, TTF-1).

This case is unique for its exceptionally long disease-free interval and highlights the diagnostic challenge posed by ccRCC metastases mimicking primary thyroid neoplasms. It underscores the critical importance of a thorough medical history, even for remote malignancies, and the value of comprehensive pathological and immunohistochemical evaluation in guiding accurate diagnosis and management. The patient achieved excellent long-term disease-free survival following surgical resection, reinforcing that aggressive local therapy for solitary thyroid metastases from ccRCC can lead to favorable outcomes and impact future practice by advocating for vigilant, long-term surveillance in ccRCC patients.