2017 Volume 66 Issue 5 Pages 576-581
Background: Metastasis of cancers to the thyroid gland is rare. Renal cell carcinoma is the most frequent source of metastatic cells to the thyroid gland. We report a case of DPP IV-positive metastatic renal cell carcinoma to the thyroid gland. Case: A 50-year-old woman had undergone a right radical nephrectomy for clear cell renal cell carcinoma in November 2009. The patient presented with a 2-cm solitary palpable mass in the right lower pole of the thyroid gland on ultrasonography in September 2014. Fine needle aspiration cytology showed cell clusters and isolated cells with large and hyperchromatic nuclei of varying sizes, conspicuous nucleoli, and abundant granular cytoplasm. Tumor cells showed strong staining of DPP IV. The cytological diagnosis was poorly differentiated carcinoma. The patient underwent a right thyroid lobectomy. The histopathological diagnosis was metastatic clear cell renal cell carcinoma. Conclusion: Differential diagnosis of primary and metastatic thyroid carcinomas is often difficult. DPP IV staining of cytological specimens is a supplemental marker for distinguishing thyroid carcinoma from benign thyroid lesions. However, metastatic renal cell carcinoma to the thyroid gland also shows strong staining for DPP IV.
