Coloured 3D computer tomography (CT) scan of the abdomen of a patient with a tumour in the right kidney (at left). This is renal cell carcinoma, the most common form of malignant (cancerous) tumour found in the kidney. Carcinomas arise from the epithelial tissues of an organ. This cancer is most common in those over 60, with males being twice as likely as females to be affected. Risk factors include, smoking, high blood pressure and long term dialysis. Renal cell carcinoma is usually not found until the tumour is quite large. Treatment is with surgical removal of the tumour or kidney. The cancer responds poorly to chemotherapy and radiotherapy.