The kidneys are a pair of organs on either side of the spine in the lower abdomen. Each kidney is about the size of a fist.
Your kidneys are part of the urinary tract. They make urine by removing wastes and extra water from your blood.
Urine collects in a hollow space (renal pelvis) in the middle of each kidney. Urine passes from your renal pelvis into your bladder through a long tube called a ureter. Urine leaves your bladder through a shorter tube (the urethra).
Your kidneys also make substances to help control blood pressure and to make red blood cells.
Attached to the top of each kidney is an adrenal gland. A layer of fatty tissue and an outer layer of fibrous tissue surround the kidney and adrenal gland.
Cancer begins in cells, the building blocks that make up tissues. Tissues make up the organs of the body.
Normal cells grow and divide to form new cells as the body needs them. When normal cells grow old or get damaged, they die, and new cells take their place.
Sometimes, this process goes wrong. New cells form when the body doesn’t need them, and old or damaged cells don’t die as they should. The buildup of extra cells often forms a mass of tissue called a growth or tumor.
Tumors in the kidney can be benign (not cancer) or malignant (cancer). Benign tumors are not as harmful as malignant tumors:
Benign tumors (such as cysts)
- are usually not a threat to life
- can be treated or removed and usually don’t grow back
- don’t invade the tissues around them
- don’t spread to other parts of the body
- may be a threat to life
- usually can be removed but can grow back
- can invade and damage nearby tissues and organs
- can spread to other parts of the body
Kidney cancer cells can spread by breaking away from the kidney tumor. They can travel through lymph vessels to nearby lymph nodes. They can also spread through blood vessels to the lungs, bones, or liver. After spreading, kidney cancer cells may attach to other tissues and grow to form new tumors that may damage those tissues.
When you get a diagnosis of kidney cancer, it’s natural to wonder what may have caused the disease. Doctors usually can’t explain why one person gets kidney cancer and another doesn’t.
However, we do know that people with certain risk factors may be more likely than others to develop kidney cancer. A risk factor is something that may increase the chance of getting a disease.
Studies have found the following risk factors for kidney cancer:
- Smoking: Smoking tobacco is an important risk factor for kidney cancer. People who smoke have a higher risk than nonsmokers. The risk is higher for those who smoke more cigarettes or for a long time.
- Obesity: Being obese increases the risk of kidney cancer.
- High blood pressure: Having high blood pressure may increase the risk of kidney cancer.
- Family history of kidney cancer: People with a family member who had kidney cancer have a slightly increased risk of the disease. Also, certain conditions that run in families can increase the risk of kidney cancer.
- Von Hippel-Lindau (VHL) syndrome: VHL is a rare disease that runs in some families. It’s caused by changes in the VHL gene. People with a changed VHL gene have an increased risk of kidney cancer. They may also have cysts or tumors in the eyes, brain, or other parts of the body. Family members of those with VHL can have a test to check for a changed VHL gene.
Many people who get kidney cancer have none of these risk factors, and many people who have known risk factors don’t develop the disease.