Kidney cancer with thyroid metastasis combined with thyroid carcinoma, a case report

BACKGROUND: Thyroid cancer is the most common malignant tumor of the endocrine system. There have been some reports on kidney cancer with thyroid metastasis. However, kidney cancer has rarely been detected during thyroid cancer surgery. CASE PRESENTATION: We present a rare case of kidney cancer with thyroid metastasis, combined with thyroid carcinoma. A 66-year-old woman was admitted to our hospital in September 2021 due to enlarged left thyroid nodules for two years. The patient was diagnosed with a left thyroid nodule on physical examination in 2012. Extended radical resection of the thyroid cancer was performed. Intraoperatively, two thyroid lesions were identified. Thus, the patient was definitively diagnosed with kidney cancer with thyroid metastasis and papillary thyroid carcinoma. Furthermore, two metastatic nodules due to kidney cancer and one metastatic lymph node lesion due to thyroid cancer were found in the loose connective tissue adjacent to the thyroid. CONCLUSIONS: Kidney cancer with thyroid metastasis and thyroid carcinoma rarely co-occur, and it is difficult to identify the primary tumor. Although clinical examination methods are increasingly updated, the past medical history and physical examination are still very important.