Renal pelvis and ureter cancer is a rare type of cancer that originates in the renal pelvis or ureter, which are parts of the urinary system. The renal pelvis is the funnel-shaped structure within the kidney that collects urine, while the ureter is the tube that carries urine from the kidney to the bladder. This cancer can develop due to various factors, including genetic mutations, exposure to certain chemicals, and chronic inflammation.