TTF1 and nonpapillary renal cell carcinoma: Immunohistochemical diagnosis is a valuable method for diagnosing thyroid metastasis from ccRCC.[16] The metastatic tumor cells are negative for thyroglobulin, calcitonin, or TTF-1, but positive for CD10 and vimentin, which are in agreement with the postoperative immunohistochemistry report in our case.