Metastatic carcinoma to the thyroid gland from renal cell carcinoma: role of ultrasonography in preoperative diagnosis

BACKGROUND Patients with metastases to the thyroid from renal cell carcinoma (RCC) that need surgical management are not many and unfamiliar to clinicians and thyroid endocrinologists. Therefore, little information is available on ultrasonographic features of metastatic carcinoma in the thyroid. The strategic value of ultrasound in preoperative surgical planning for patients with thyroid nodules has become increasingly appreciated. The purposes of this article are to clarify the ultrasound characteristics of metastatic carcinoma to the thyroid from RCC by evaluating many patients in one institute, and to investigate the role of ultrasonography in preoperative diagnosis. METHODS Ten patients with these carcinomas who had undergone surgical management were investigated clinically and ultrasonographically. Ultrasonographic features to be evaluated were the form of involvement in the thyroid, size, shape, pattern, calcifications, vascularity, and tumor thrombus. Clinical features were previous history of RCC, serum thyroglobulin levels, cytology, preoperative diagnosis, and surgery. RESULTS Ultrasonographic features of these carcinomas were more likely to involve a solitary, irregular, and solid without calcifications, and prominent intra-tumoral vascularity and tumor thrombus in the vein. These patients tended to be older, and to have relatively late recurrence in the thyroid, RCC in the right kidney as the primary site, and relatively low serum thyroglobulin levels. CONCLUSIONS Metastatic carcinomas to the thyroid from RCC presented highly characteristic features on ultrasonography. These ultrasonographic features combined with cytological findings and previous medical history of RCC can provide the optimal process for the preoperative diagnosis of such patients.