Cancer is when cells in the body grow out of control, often forming a mass or tumor. In upper urinary tract cancer, abnormal cells are found in the:
Female urinary tract
Male urinary tract
- Renal pelvis (where urine collects in the kidneys before it travels to the ureters and bladder)
- Renal calyces (spaces deep in the kidneys)
- Ureters (thin tubes, made of muscle, which move urine from the kidney to the bladder)
Cancers of the upper urinary tract are relatively rare. In 2015, about 3,100 Americans will be diagnosed with this cancer. The most common of all upper urinary tract cancers are those found in the renal pelvis and renal calyces. Cancer in the ureters makes up about a quarter of all upper urinary tract cancers.
Tumors of the renal calyces, renal pelvis and ureters start in the layer of tissue that lines the bladder and the upper urinary tract, called the urothelium. Cancer that starts in the urothelium is called urothelial (or transitional cell) cancer. This is the most common type of cancer found in the bladder, as well. Because many of the organs in the urinary system share common cells, cancers found in these organs often look and act alike.
Parts of the kidney
The urothelium is special in the way that it swells and shrinks to push urine through the urinary tract. Because it is in direct contact with the urine, this lining is exposed to chemicals (carcinogens) filtered out of the blood by the kidneys. These chemicals can cause cells to change and grow out of control as cancer.
Because the bladder stores urine, it may be at greater risk for cancer than other parts of the upper tract. Its cells are exposed to harmful substances for a longer time. When urine has a high percent of harmful chemicals, cancer may also grow in the kidney or ureters.
To understand cancer of the ureter and renal pelvis, it helps to know how these organs normally work.