Understanding Kidney Cancer

What Is Kidney Cancer?

Last updated and reviewed on June 13, 2026.

Kidney cancer is a disease where cells in the kidney start to grow out of control. Normally, your body makes new cells only when it needs them, and old or damaged cells die off. With cancer, something goes wrong inside the cell's DNA, its instruction manual, and cells begin multiplying without stopping. Over time, those extra cells build up into a mass called a tumor. When that tumor forms in the kidney, it is called kidney cancer. Kidney cancer is one of the ten most common cancers in both men and women in the United States.

What Is the Kidney?

Most people are born with two kidneys, one on each side of the spine, located just below the rib cage in the back of the abdomen. Each kidney is about the size of your fist. The kidneys are part of the urinary system, which also includes the ureters (tubes that carry urine from the kidneys to the bladder), the bladder, and the urethra (the tube through which urine leaves the body).

The kidneys do several important jobs:

• They filter waste products and extra water out of the blood to make urine.
• They help control blood pressure by releasing a hormone called renin.
• They produce a hormone called erythropoietin (EPO) that tells the bone marrow to make red blood cells.
• They help keep the body's balance of salt, minerals, and fluids.
• They activate vitamin D, which keeps bones strong.

Each kidney is made up of millions of tiny filtering units called nephrons. Each nephron has a small cluster of blood vessels (called a glomerulus) and a tiny tube (called a tubule) that collects the filtered fluid. Most kidney cancers start in the cells lining those tubules.

Source: American Cancer Society.

How Does Kidney Cancer Start?

Kidney cancer starts when the DNA inside a kidney cell gets damaged or changed in a way that makes the cell grow and divide without stopping. DNA is the chemical "code" inside every cell that controls how it behaves. When DNA instructions are damaged or mutated, cells can ignore normal signals to stop growing, and a tumor begins to form.

These DNA changes can happen by chance, or they can be caused by things a person is exposed to over time, such as tobacco smoke or certain chemicals. In some families, mutations that raise the risk of kidney cancer are passed down from parent to child. In most cases, though, no single clear cause is found.

As a kidney tumor grows, it can start to affect the kidney's normal function. In some cases, it can also grow into nearby tissues or send cancer cells through the bloodstream or lymph system to other parts of the body, a process called metastasis.

Where Does Kidney Cancer Start?

Most kidney cancers start in the renal cortex, which is the outer layer of the kidney where most of the nephron tubules are found. The most common type of renal cell carcinoma begins in the cells that line the tiny tubules inside the kidney.

A less common but important type, urothelial carcinoma of the renal pelvis, starts in the renal pelvis, the inner part of the kidney where urine collects before it drains down the ureter to the bladder. These tumors are more similar to bladder cancer in how they behave and how they are treated.

Cancer can also develop in only one kidney or, more rarely, in both kidneys at the same time. The location within the kidney can affect how easy it is to surgically remove the tumor and whether nearby structures like the adrenal gland or major blood vessels are involved.

How Does Kidney Cancer Affect the Body?

In its early stages, kidney cancer often causes no symptoms at all. Many people feel completely well while a small tumor grows quietly inside the kidney. As the tumor gets bigger, it can affect the kidney's function and cause symptoms like blood in the urine, back pain, or a lump in the side or back.

If the cancer spreads beyond the kidney, it can affect other organs. Kidney cancer most commonly spreads to the lungs, bones, brain, liver, and adrenal glands. When cancer spreads to these places, it can cause symptoms like shortness of breath, bone pain, headaches, or unexplained weight loss. Even when cancer has spread, modern treatments can often control it for an extended period.

What Are the Types of Kidney Cancer?

There are several types of kidney cancer. Knowing the type helps doctors choose the best treatment.

Renal Cell Carcinoma (RCC) This is by far the most common type, making up about 90% of all kidney cancers in adults. RCC itself has several subtypes:

• Clear cell RCC: The most common subtype, making up about 70–75% of all RCC cases. The cancer cells look pale or clear under a microscope because they are full of fat and glycogen. Clear cell RCC is linked to changes in the VHL gene.
• Papillary RCC: The second most common subtype, accounting for about 10–15% of cases. The cells form tiny finger-like projections called papillae. There are two subtypes: type 1 (tends to grow more slowly) and type 2 (often more aggressive).
• Chromophobe RCC: Makes up about 5% of RCC cases. The cancer cells have a distinctive appearance under the microscope. This type generally has a better outlook than clear cell or papillary RCC.
• Collecting duct RCC and other rare subtypes: These are uncommon and often more aggressive.

Transitional Cell Carcinoma (Urothelial Carcinoma) of the Renal Pelvis. This type starts in the renal pelvis, the funnel-shaped area where urine drains out of the kidney. It makes up about 5–10% of kidney cancers and behaves more like bladder cancer than renal cell carcinoma. It is strongly linked to cigarette smoking and chemical exposures.

Wilms Tumor (Nephroblastoma). This is the most common type of kidney cancer in children, usually affecting kids between the ages of 3 and 4. It is rare in adults. Wilms tumor responds very well to treatment, and cure rates are high.

Renal Sarcoma. This is a rare type that starts in the connective tissue (the supporting framework) of the kidney. It makes up less than 1% of kidney tumors.

What Are the Related Disorders to Kidney Cancer?

Some medical conditions are associated with a higher risk of kidney cancer or may be confused with it.

• Angiomyolipoma: A benign (non-cancerous) tumor made of fat, muscle, and blood vessels. It can grow in the kidney and sometimes looks like cancer on imaging. It is more common in people with tuberous sclerosis.
• Oncocytoma: Another benign kidney tumor that can look similar to RCC on a CT scan. Biopsy or surgery is sometimes needed to tell it apart from cancer.
• Tuberous sclerosis complex (TSC): A genetic condition that causes non-cancerous tumors to grow in many organs, including the kidneys. People with TSC have a higher risk of developing certain kidney tumors.
• Polycystic kidney disease (PKD): A condition where fluid-filled sacs (cysts) grow in the kidneys. People with PKD may have a slightly higher risk of kidney cancer.
• Acquired cystic kidney disease: People on long-term dialysis for kidney failure may develop kidney cysts and have a higher risk of kidney cancer.

What Are the Genetic and Risk Factors?

Most kidney cancers develop in people with no family history of the disease and no known genetic mutation. However, some inherited gene changes can significantly raise a person's risk. The most well-known hereditary condition linked to kidney cancer is Von Hippel-Lindau (VHL) syndrome, caused by mutations in the VHL gene. People with VHL syndrome are at high risk for clear cell RCC, often developing multiple tumors in both kidneys.

Other hereditary conditions linked to kidney cancer include:

• Hereditary papillary renal cell carcinoma (HPRC): Caused by mutations in the MET gene; raises the risk of papillary type 1 RCC.
• Birt-Hogg-Dubé (BHD) syndrome: A genetic condition that raises the risk of chromophobe and other types of RCC, as well as skin and lung problems.
• Hereditary leiomyomatosis and renal cell cancer (HLRCC): Caused by mutations in the FH gene; linked to papillary type 2 RCC.
• Succinate dehydrogenase (SDH)-related kidney cancer: Rare mutations in SDH genes can raise kidney cancer risk.

Non-hereditary risk factors include smoking, obesity, high blood pressure, long-term dialysis, and workplace exposure to certain chemicals. These are covered in more detail in the Risk Factors guide.

What Are the Related Cancers to Kidney Cancer?

Kidney cancer shares connections with several other cancers. Urothelial carcinoma of the renal pelvis is closely related to bladder cancer and ureter cancer, since all three start in the same type of cells (urothelial cells) that line the urinary tract. People who have had bladder cancer or ureter cancer have a higher risk of developing urothelial tumors in the kidney, and vice versa.

Kidney cancer can also be part of hereditary cancer syndromes that increase a person's risk for other cancers. For example, people with VHL syndrome have higher risks for tumors of the eye, brain, spinal cord, adrenal glands, and pancreas in addition to kidney cancer. Because of these connections, people with a personal or family history of certain cancers may benefit from genetic counseling and regular monitoring.

Sources:

1. American Cancer Society. What Is Kidney Cancer? https://www.cancer.org/cancer/types/kidney-cancer/about/what-is-kidney-cancer.html
2. National Cancer Institute. Renal Cell Cancer Treatment (PDQ) – Patient Version. https://www.cancer.gov/types/kidney/patient/kidney-treatment-pdq
3. Newly Diagnosed https://www.kidneycancer.org/newly-diagnosed/