There are two kidneys, one on each side of the spine, above the waist. The kidneys clean the blood to take out waste and make urine. Urine collects in the renal pelvis, the area at the center of the kidney, and then passes through the ureter, into the bladder, and out of the body. The kidneys also make hormones that help control blood pressure and signal the bone marrow to make red blood cells when needed.
There are three main types of kidney cancer. Renal cell cancer is the most common type in adults and Wilms tumors are the most common in children. These types form in the tissues of the kidney that make urine. Transitional cell cancer forms in the renal pelvis and ureter in adults.
The bladder is a hollow organ in the lower part of the abdomen that stores urine until it is passed out of the body.
The most common type of bladder cancer is transitional cell carcinoma, which begins in urothelial cells that line the inside of the bladder. Urothelial cells are transitional cells, which are able to change shape and stretch when the bladder is full. This type of cancer is also called urothelial carcinoma. Other types of bladder cancer include squamous cell carcinoma (cancer that begins in thin, flat cells lining the bladder) and adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids).
