A case of renal cell carcinoma with metastasis to the thyroid gland and concomitant early gastric cancer.

Metastatic lesions from renal cell carcinoma are commonly recognized in the lung and bone, however, thyroid metastasis has rarely been reported in the literature. We present herein a case of a man with lung and thyroid metastatic tumors from renal cell carcinoma. Although making a preoperative diagnosis of thyroid metastasis is difficult because there is no established diagnostic criteria, we were able to identify this thyroid lesion as a metastatic tumor from renal cell carcinoma by the pathological findings. Interestingly, hypercalcemia was recognized in this patient whose serum parathyroid hormone (PTH) level was not increased. Moreover, this patient also had early gastric cancer simultaneously, being a so-called 'double cancer'. After surgical resection of the right kidney and stomach, interferon was administered without any efficacy against the metastatic lesions of the lung and thyroid gland.