Renal cancer starts in the cells of the kidney
Renal cancer (also called kidney cancer) begins when cells in one or both kidneys grow in an uncontrolled way. The kidney is a bean-shaped organ about the size of your fist that filters waste from your blood to make urine. When cells in the kidney tissue mutate, they can form a tumor. If that tumor is malignant—meaning it can spread to other parts of the body—it is cancer.
Most renal cancers are found in the outer layer of the kidney, called the renal cortex. The most common type is clear cell renal cell carcinoma, which accounts for about 70 to 80 percent of all kidney cancers. Other types include papillary renal cell carcinoma, chromophobe renal cell carcinoma, and oncocytoma (which is usually benign). The type matters because different cancers grow at different speeds and respond differently to treatment.
Renal cancer often has no symptoms in its early stages, which is why many cases are found by accident during imaging for another reason—a CT scan, ultrasound, or MRI done for a different problem. When symptoms do appear, they typically include blood in the urine, persistent pain in the side or lower back, or a lump you can feel in the abdomen.
Key Takeaways
- Renal cancer develops when cells in the kidney grow uncontrollably and can form a tumor that spreads to other organs.
- Clear cell renal cell carcinoma is the most common type, accounting for roughly 70 to 80 percent of kidney cancer cases.
- Early-stage renal cancer often causes no symptoms, so many cases are discovered during imaging tests done for other reasons.
- Risk factors include smoking, obesity, high blood pressure, and a family history of kidney cancer.
- Doctors stage renal cancer by size, whether it has spread to lymph nodes, and whether it has metastasized to distant organs.
How renal cancer develops and spreads
Renal cancer develops when DNA mutations occur in kidney cells. These mutations cause the cells to ignore the body's normal signals to stop growing and die. Instead, the cells divide repeatedly and form a mass. Researchers do not yet fully understand why these mutations happen in some people and not others, but certain factors increase the risk.
Smoking is one of the strongest known risk factors—smokers have roughly twice the risk of nonsmokers. Obesity and high blood pressure also increase risk. People with a family history of kidney cancer, those with certain genetic syndromes (like von Hippel-Lindau disease), and those with chronic kidney disease face higher risk as well. Men are diagnosed with renal cancer about twice as often as women, though doctors are not certain why.
When renal cancer spreads, it typically moves first to nearby lymph nodes, then to distant organs. The lungs are the most common site for spread, followed by the bones, liver, and brain. A cancer that has spread beyond the kidney is called metastatic renal cancer and is harder to treat than cancer confined to the kidney itself.
Stages of renal cancer and what they mean
Doctors stage renal cancer using a system that describes the size of the tumor, whether it has invaded surrounding tissue, and whether it has spread. The stage determines treatment options and prognosis—the likely course of the disease.
Stage 1 tumors are small (less than 7 centimeters) and confined to the kidney. Stage 2 tumors are larger but still within the kidney. Stage 3 cancers have spread to nearby lymph nodes or blood vessels but not to distant organs. Stage 4 means the cancer has spread to distant organs or invaded surrounding structures like the colon or diaphragm. Stage 4 renal cancer is considered advanced and is treated differently than earlier stages.
Staging also considers the cancer's grade—how abnormal the cells look under a microscope. Higher-grade cancers tend to grow faster and are more likely to spread. Your doctor will use both the stage and grade, along with other factors like your overall health, to recommend a treatment plan.
Symptoms that may appear as the cancer grows
In early stages, renal cancer usually causes no symptoms at all. Many people have no idea they have it until a scan done for another reason reveals a kidney tumor. This is one reason renal cancer is sometimes called a "silent killer."
As the cancer grows, symptoms may include blood in the urine (which may be visible or only detectable by a lab test), pain or pressure in the side or lower back that does not go away, a lump or mass you can feel in the abdomen, unexplained weight loss, fever that is not caused by infection, or fatigue. Some people experience night sweats or high blood pressure. These symptoms can be caused by many other conditions, so having them does not mean you have cancer—but they are worth discussing with your doctor.
If renal cancer spreads to the lungs, you might develop a persistent cough or chest pain. Spread to the bones can cause bone pain. These symptoms of metastatic disease often bring people to the doctor, even if they had no symptoms from the original kidney tumor.
How doctors find and confirm renal cancer
Renal cancer is usually discovered through imaging. If your doctor suspects a kidney problem, they may order an ultrasound (which uses sound waves to create an image), a CT scan (which takes detailed cross-sectional pictures), or an MRI (which uses magnetic fields). These tests can show the size and location of a tumor and whether it appears to have spread.
If imaging shows a suspicious mass, your doctor may perform a biopsy—removing a small sample of tissue with a needle to examine under a microscope. A biopsy confirms whether the mass is cancer and what type it is. Not all kidney masses need a biopsy; sometimes imaging alone is enough to diagnose renal cancer, especially if the tumor has typical features.
Once cancer is confirmed, your doctor will order additional tests to see if it has spread. These may include a chest CT (to check the lungs), bone scans, or brain imaging. Blood tests may also be done to check kidney function and look for markers that can indicate how advanced the cancer is.
Treatment options depend on stage and overall health
Treatment for renal cancer varies based on the stage, size, and location of the tumor, as well as your age and overall health. For small tumors confined to the kidney, surgery is the primary treatment. A surgeon may remove the entire kidney (radical nephrectomy) or just the tumor and a margin of surrounding tissue (partial nephrectomy). Partial nephrectomy is preferred when possible because it preserves kidney function.
For tumors that cannot be removed surgically, or for people who are not healthy enough for surgery, other options include ablation (using heat or cold to destroy the tumor), radiation therapy, or targeted drug therapy. Targeted drugs work by blocking the signals that allow cancer cells to grow. For advanced renal cancer that has spread, immunotherapy drugs—which help the immune system recognize and attack cancer cells—have become increasingly important in recent years.
Chemotherapy is less commonly used for renal cancer than for some other cancers, because kidney cancer cells are often resistant to chemotherapy drugs. Your doctor will discuss which treatments are most likely to work for your specific cancer and what side effects to expect.
Living with renal cancer after treatment
After treatment, you will need regular follow-up appointments and imaging to watch for recurrence—cancer returning in the kidney, nearby tissue, or distant organs. How often you are monitored depends on the stage of your cancer and how it responded to treatment. Early-stage cancers that are completely removed have a better outlook than advanced cancers, but recurrence is possible even years later.
If renal cancer does return or spread, your doctor may recommend additional treatment. Some people live for many years with metastatic renal cancer, especially with newer drug treatments available. Others may have a shorter survival time. Survival depends on many factors, including the stage at diagnosis, the type of cancer, how well it responds to treatment, and your overall health.
Clinical trials are ongoing for new renal cancer treatments. If standard treatments are not working or if you want to explore newer options, ask your doctor whether a clinical trial might be right for you. Participating in a trial gives you access to cutting-edge treatments while also contributing to research that may help future patients.
Frequently Asked Questions
Can you live a normal life with one kidney?
Yes. Your kidneys filter waste, but you only need one to do that job adequately. Many people live normal lifespans with one kidney—whether from surgery, donation, or birth. You may need to monitor kidney function and avoid certain medications, but most daily activities are unaffected. Your doctor will advise you on any restrictions.
Is renal cancer hereditary?
Most renal cancer is not inherited. However, certain genetic syndromes like von Hippel-Lindau disease, hereditary papillary renal cell carcinoma, and Birt-Hogg-Dubé syndrome do increase kidney cancer risk and run in families. If you have a family history of kidney cancer, talk to your doctor about whether genetic testing or screening might be appropriate.
What is the difference between renal cancer and bladder cancer?
The kidney filters blood and stores urine; the bladder stores urine until you urinate. Cancer can start in either organ. Renal cancer is typically treated with surgery to remove the kidney or tumor. Bladder cancer is often treated with surgery to remove the bladder or with chemotherapy and radiation. The two cancers have different risk factors, symptoms, and treatment approaches.
Can renal cancer be prevented?
You cannot prevent renal cancer entirely, but you can reduce your risk by not smoking, maintaining a healthy weight, controlling blood pressure, and limiting alcohol. These steps lower your risk of kidney cancer and many other diseases. If you have a family history of kidney cancer or a genetic syndrome, talk to your doctor about screening options.
How often should I be screened for renal cancer?
Routine screening for kidney cancer is not recommended for people without symptoms or risk factors. However, if you have a family history of kidney cancer, a genetic syndrome, or chronic kidney disease, your doctor may recommend periodic imaging. Talk to your doctor about what screening, if any, makes sense for your situation.