Nasopharyngeal metastasis of follicular carcinoma of the thyroid with extensive clear cell change: a case report.

Thyroid carcinoma metastatic to the maxillofacial area is extremely rare. Other carcinomas can metastasize to this area, but very few cases of follicular thyroid carcinoma metastasizing to the nasopharynx have been reported. Carcinoma from the kidney, liver, large bowel, prostate, and thyroid are known to have the potential for clear cell differentiation, and all of them can metastasize to the sinonasal area. Histochemical and immunohistochemical evaluations, along with clinical details, are useful in distinguishing metastases of these clear cell tumors from primary sinonasal tumors. In this article we describe a rare case of metastatic thyroid carcinoma with clear cell change mimicking metastatic renal cell carcinoma in the nasopharynx.