Renal pelvis cancers are cancers that start in the middle of a kidney, where urine collects before going to the bladder. Ureter cancers start in one of the tubes that connect the kidney to the bladder. Cancer is a disease caused by a group of abnormal cells that grow and multiply without stopping. As these cells grow and multiply, they form a tumor or lump. The tumor cells replace the normal cells of the organ. Tumor cells crowd out the normal cells. This leaves fewer healthy cells to do the job of that organ. The tumor can also block passages that help the organ work. Tumor cells can grow from one organ into nearby tissues and other organs. They can also travel through the blood and lymph to other parts of the body and form more tumors. These tumors are called metastases.
Renal pelvis and ureter cancers start in the cells that line the inside of these structures. The lining tissue is made up of two types of cells, transitional cells and squamous cells. Most renal pelvis and ureter cancers start from transitional cells. Cancers that start from this type of cell are called, “transitional cell” cancers. Another name for renal pelvis and ureter cancer is urothelial cancer. Tumor cells grow in the lining tissue, and can invade through the layers of the renal pelvis or ureter, and spread to lymph nodes and other tissues nearby.
Renal pelvis and ureter cancers are not common cancers. When someone has one of these cancers, the person is also examined for tumors in the bladder. 30% to 50% of patients with cancer of the renal pelvis or ureter have or will have bladder cancer at some time.