Renal Cell Carcinoma Metastasis to Thyroid Gland Associated with PapillaryThyroid Carcinoma: A Case Report and Review of the Literature

Metastatic thyroid gland tumor is an uncommon finding in clinical practice. We report a case of metastatic renal cell carcinoma (RCC) to the thyroid gland, associated with a Papillary Thyroid Carcinoma (PTC), in a patient who had undergone left nephrectomy for RCC 6 years earlier and operated on in our Institution for a multinodular goiter disease. Immunohistochemistry can be helpful for the differential diagnosis. Metastatic cells of RCC were positive for CD10 and vimentin and negative for thyroglobulin, calcitonin, and TTF-1. Papillary carcinoma cells were positive for Cytokeratin 19, galectin-3, CD56 and Hector Battifora Mesothelial cell monoclonal antibody-1. The association between papillary thyroid carcinoma and RCC is a rare condition and maybe must not be considered a fortuitous development of 2 different neoplasms.