Although our clinical experience remains limited due to the complexity of obtaining serial samples at the time of progression in kidney cancer patients, our clinical data showed that CD31/CD10-stained renal cancer cells could be found in more than 50% of the primary tumors in patients presenting RCC, as well as in some patients who progressed under sunitinib therapy while being absent from patients responding to sunitinib. The gene discussed is PECAM1; the disease is renal cell carcinoma.