Tumor to tumor metastasis: report of two cases and review of the literature.

Tumor-to-tumor metastases are uncommon. The most frequent donor tumor is lung cancer, while renal cell carcinoma (RCC) is by far the most common recipient. In this report, a carcinoma of the uterine cervix metastasizing to an RCC and a urothelial carcinoma of the urinary bladder metastasizing to a solitary fibrous tumor of the pleura are described. No similar cases have been found in the accessible literature. These cases are discussed and the findings are correlated with the data of the literature.