[Tumor-to-tumor metastasis in a renal carcinoma: A rare and surprising event]. / Métastase d'une tumeur primitive dans un carcinome rénal : un évènement rare et surprenant.

Tumor-to-tumor metastasis is a very rare event. We report three cases of tumor metastasizing in a clear cell renal cell carcinoma: two breast carcinomas and a sigmoid carcinoma. So we objectified a prevalence of 1.5% of renal tumors in our series. It's a rare situation but to be considered in daily practice because it changes oncological management offered to the patient. According to the literature, clear cell renal cell carcinoma is the most common tumor recipient of metastasis. Several physiopathological mechanisms can explain this phenomenon, but many of them are still unknown. A better understanding of this phenomenon makes it possible to improve the diagnosis and thus the management of patients with several cancers.