Recently, it has been described that metastatic tumor in the thyroid should be diagnosed based on rich vascularity, abundant extravasated erythrocytes, pseudofollicular spaces filled with blood, negativity for thyroglobulin, and positivity for CD10 and positivity for the renal cell carcinoma marker carbonic anhydrase IX [15]. This evidence concerns the gene CA9 and hereditary clear cell renal cell carcinoma.