AUA Summit - What is a Renal Mass and What is a Localized Renal Tumor?
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What is a Renal Mass and What is a Localized Renal Tumor?

The word renal means kidney. The words "tumor" and "mass" mean abnormal growths in the body. A renal mass, or tumor, is an abnormal growth in the kidney. Some renal masses are benign (not cancerous) and some are malignant (cancerous).

One in four renal masses are benign. Smaller masses are more likely to be benign. Larger masses are more likely to be cancerous. Some tumors can be slow to grow while some can be aggressive. Aggressive tumors form, grow and spread very quickly.

Most diagnosed kidney growths are small and localized masses. Localized means that the tumor has not spread out from where it first started. Around 40% of kidney cancers are localized renal masses. Masses may be solid or cystic (having fluid). Most cystic masses are benign. 

What do we Know about Kidney Cancers?

Kidney and renal pelvis cancers are the 11th leading cause of cancer death in the U.S. Kidney cancer is 8th on the list of the 10 most common types of cancer. Almost all of the kidney cancers in the U.S. are renal cell carcinomas (RCC). These cancers form in the lining of the small tubes in the kidney.

Doctors are able to diagnose kidney cancer earlier because of better testing. Kidney cancer is more common in men than women. More men than women die from the disease. Kidney cancer is more common in African Americans, American Indians and Alaskan Native people. You can get kidney cancer at any age. But, it is more common in older people (those greater than 75 years old).

There will be more than 76,000 new cases of kidney cancer in the U.S. in 2021. Of those cases, nearly 14,000 people will likely die from the disease. The earlier the cancer is diagnosed-the better the chances of survival. The five-year survival rate for all kidney cancers is about 74%. If the cancer spreads over the body, then this rate falls to about 12%. The five-year survival for localized kidney and renal pelvis cancer is 92.5%.

Around the world, over 300,000 people get kidney cancer each year. Half of those people will die from the disease. But, less people are dying each year from the disease.

Types of Renal Tumors

Renal tumors are grouped by where they start growing and by their structure. The main classes of tumors are:

  • Renal Cell Carcinomas (RCC). These are the most common malignant kidney tumors. They are found in the lining of the small tubes in the kidney. RCC may form as a single tumor within a kidney. It can also form two or more tumors in one kidney. 
  • Benign renal tumors. There are about 9 different types of tumors in this class. Some can grow quite large. But most are non-cancerous and do not spread to other organs. 
  • Wilms tumor. Wilms tumors almost always are found in children and are rarely found in adults.

Where are the Kidneys and What are they for?

The kidneys are two bean-shaped organs near the middle of the back. There is one kidney below the rib cage on each side of the spine. Each kidney is about the size of a fist.Our kidneys' main job is to filter the blood. The kidneys remove water and waste from our blood in the form of urine. Urine then leaves our body by way of the bladder and the urethra. As a filter, the kidneys:

  • Detoxify (clean) our blood
  • Balance fluids
  • Maintain electrolyte levels (e.g., sodium, potassium, calcium, magnesium, acid)
  • Remove waste (as urine)

The kidneys also make hormones that help to:

  • Keep blood pressure stable
  • Make red blood cells
  • Make bones stay strong


Over half of renal tumors are found by chance and may have no symptoms. They often are found when your doctor is doing a test for other health problems. Tumors found in this way are more likely localized to the kidney. These types of tumors have good outcomes. Most renal masses have no symptoms in the early stages. But, if there are symptoms, they will most likely be:

  • Hematuria (blood in urine)
  • Flank pain between the ribs and hips
  • Low back pain on one side (not caused by injury) and that does not go away
  • Loss of appetite
  • Weight loss not caused by dieting
  • Fever not caused by an infection and that does not go away
  • Anemia (low red blood cell count)


Doctors do not know what causes kidney cancer. But, they do know there are certain risk factors that increase your chance of getting kidney cancer. They are:

  • Smoking (male smokers have a higher risk than female smokers)
  • Drinking a lot of alcohol
  • Obesity, poor diet
  • Family history of high blood pressure
  • Being on kidney dialysis
  • Workplace exposure to chlorinated chemicals 
  • Heredity (some kidney cancers are found in multiple family members)

How can you lessen the risk for kidney cancer?

Some actions may help to reduce the risk of kidney tumors:

  • Stop smoking
  • Limit alcohol intake
  • Eat fruits and vegetables like broccoli, brussel sprouts, cabbage, collard greens and kale
  • Add fatty fish into your diet such as salmon, tuna and sardines
  • Maintain a healthy diet
  • Exercise regularly, it will help prevent obesity and hypertension


There are no routine lab tests to find kidney cancer. Often tumors are found during genetic screening or when you see a doctor about another problem. If your doctor thinks you have a kidney tumor, he/she might send you to see a urologist. A urologist is a doctor who specializes in the genitourinary system. When you see your urologist, they will ask you questions about your symptoms and health. They will give you a physical exam, order lab tests and may take pictures of your body.

Some common tests and procedures for renal tumors

Your doctor may use many tests and procedures to make a diagnosis. Here are some that you might expect: 

  • Physical exam and history is when your healthcare provider checks your body and asks you questions about your health and family. He/she will check for lumps or any other unusual signs. Your health habits, past illnesses and treatments will also be discussed. 
  • Basic or complete metabolic panel (CMP), also called a blood chemistry, is used to evaluate organ function and check for certain conditions.
  • Complete Blood Count (CBC) checks for certain substances. If amounts are higher or lower than normal, that may be a sign of disease. 
  • Urinalysis checks for infection, blood and protein in your urine. 
  • Kidney function tests check how well the kidneys are working. They show if the kidneys are getting rid of waste the right way. 
  • Ultrasounds take pictures of your kidneys and organs. 

Imaging Tests:

  • CT scan (CAT scan or computed tomography) and MRI (magnetic resonance imaging) are useful for diagnosing and staging renal masses. They can show which kidney is affected, whether the cancer has spread and if other glands or organs are involved. 
  • Chest x-rays help to find out what stage your cancer is. A mass in your chest usually suggests your tumor has spread. 
  • Bone scans may be done if you have bone pain or neurologic (nerve) symptoms.

Renal mass biopsy may be done to find out what type of tumor you may have. A biopsy is when cells or tiny parts of an organ are removed and studied. A pathologist views the sample under a microscope. The biopsy will show if the tumor started in another part of your body or if it started in the kidney. A biopsy may also tell if there is an infection, such as an abscess. It can help find cancer and make better treatment choices.


Grade and stage are two important ways to measure and describe how cancer develops. A tumor grade tells how aggressive the cancer cells are. A tumor stage tells how much the cancer has spread.


Your healthcare provider may use a special grading system for your kidney disease. This grading system uses numbers or letters that give details about the tumor. The grades 1 through 4 show increasing severity with "1" being the lowest level and "4" the highest. A higher grade and more advanced stage usually mean larger tumor size and more aggressive tumors. Your doctor can only grade your tumor by looking at it under a microscope.


Following the American Joint Committee on Cancer (AJCC) guidelines, kidney cancer is staged using the tumor node metastases (TNM) system. This system describes the tumor in three specific ways:

  • T describes the size of the main (primary) tumor and whether it has grown into nearby areas.
  • N tells us how much it has spread to nearby (regional) lymph nodes. Lymph nodes are small bean-sized collections of immune system cells.
  • M tells us about metastasis  whether the cancer has spread (metastasized) to other parts of the body. Spread is most common to the lungs, bones, liver, brain, and far off lymph nodes.

Stage I and IItumors include cancers of any size that are only inside the kidney.

Stage III tumors are either locally invasive (T3) or involve lymph nodes (N1). This is cancer that is only found within the kidney organ.

Stage IV tumors have spread beyond the kidney into organs nearby (T4) or distant metastases (M1).

TNM Staging Categories

T describes the primary tumor. It tells us the size of the tumor and whether it has grown into nearby areas.

TX: Cannot assess primary tumor
T0: No evidence of primary tumor
T1: Tumor 7.0 cm (about 2.8 inches) or less, only in the kidney
T1a: Tumor 4.0 cm (about 1.6 inches) or less, only in the kidney
T1b: Tumor 4.0-7.0 cm, only in the kidney
T2: Tumor greater than 7.0 cm, only in kidney
T2a: Tumor greater than 7.0 cm and less than 10.0 cm, only in the kidney
T2b: Tumor greater than 10 cm (about 3.9 inches), only in the kidney
T3: Tumor grows into major veins but not into the adrenal gland and not beyond the tissue around the kidney's and adrenal glands
T3a: Tumor involves the renal vein or its branches, or perirenal and or renal sinus fat but does not grow beyond the tissue that go around the kidneys and adrenal glands
T3b: Tumor grows into the large vein that brings blood into the heart and below the diaphragm
T3c: Tumor grows into vena cava above diaphragm or reaches into the diaphragm
T4: Tumor reaches beyond the tissue around the kidney's and adrenal glands

N - This category describes the regional lymph nodes
NX: Cannot assess regional nodes
N0: No regional lymph node metastasis
N1: Metastasis in regional lymph node(s)

M - This category describes distant metastases
M0: No distant metastasis
M1: Distant metastasis


Active surveillance (AS)

Active surveillance is the least invasive treatment for small, localized renal masses. Your healthcare provider will help you decide if this is a good choice for you.

For some patients surgery is never needed. Your provider will evaluate your preferences, tumor factors and likely outcomes to see if AS is a good treatment option for you. Tumor factors will include size, stage and growth progression.

The goals of AS are to stop the spread of cancer, maintain kidney function and avoid potential side effects of treatment. There are three tracks for surveillance treatment:

More Intense AS - You will visit with your provider about every three months for tests and cross-sectional imaging, such as CT scans.
Less Intense AS - You will see your provider about every six months for tests and imaging. Tests may be both abdominal ultrasound and cross sectional imaging.
Expectant management (observation) - You will see your provider about every 12 months. Ultrasound will be used more often than other types of imaging procedures.

Partial nephrectomy and radical nephrectomy

Nephrectomy is a surgical procedure to remove all or part of the kidney. There are two types of nephrectomy for a diseased kidney  partial and radical. In a partial nephrectomy, the doctor removes the tumor or diseased part of your kidney and leaves the healthy part. Partial nephrectomy is recommended for localized renal masses and can also be done for larger tumors. When the tumor is removed, a biopsy can be done to tell whether it is cancerous or shows sign of advancing.

In a radical nephrectomy, the entire kidney is removed. A radical nephrectomy is recommended if your renal mass is very large or located near critical structures such as the blood supply to the kidney.

Laparoscopy, or robotic surgery, can be done for both types of nephrectomy instead of open surgery. During open surgery, your surgeon will make a large incision (cut) in your abdomen. During laparoscopy, your surgeon will make very small cuts in your abdomen and use a camera and long, stick-like instruments.

If your lymph nodes are affected, your surgeon will examine the node for staging and prognosis. If your adrenal glands are affected, your doctor will most likely remove the glands.


If your tumor is small ( a T1a mass less than 4 cm in size), your surgeon may consider ablation. Ablation destroys the tumor with extreme heat or cold.

  • Cryoablation (cold ablation) is when very cold gases are passed through a probe that destroys the tumor cells. 
  • Radiofrequency ablation (hot ablation) is when a thin, needle-like probe is placed through the skin to reach the tumor. Other methods such as microwave or laser ablation also may be performed. Once it is in place, an electric current is passed through the tip of the probe. This heats the tumor and destroys the cells. The probe is guided by ultrasound or CT scans.

Before ablation is done, your doctor will do a biopsy. This will help with treatment decisions. Ablation can be done by laparoscopy or by a percutaneous approach (with a needle).

It is well suited for small renal masses  those less than 3 cm. It also helps to preserve renal function and spare the kidney. The percutaneous method is better for some small renal masses because the procedure time is shorter, recovery is quicker and there is less need for pain medication.


Patients with a localized renal mass should have a urologist involved with their care. A urologist will help coordinate evaluation, counseling and management. The urologist should be part of a multidisciplinary team so that all aspects of your care are considered. Your care team might include a radiologist, urologist, neurologist, a pathologist and a medical oncologist.

Counseling would include explanations of the risks and benefits of the treatment plan and possible clinical outcomes. The best treatment plan includes your own preferences, physical condition, other illnesses, outlook and lifestyle. Decisions should include plans for the short and long term.

Genetic counseling should be offered for tumors with a familial history. There are several renal masses that are found to run in families. Patients diagnosed at the age of 46 years or younger should strongly consider genetic counseling. Ask your healthcare provider if you would benefit from genetic counseling.

After Treatment

Whatever treatment you choose, you need to stay in touch with your healthcare provider. Make sure you return for ALL follow-up appointments as directed. These checkups are important to watch for re-growth of tumors. After initial treatment, your doctor may perform many of the same tests used to diagnose your cancer.

Maintaining a healthy lifestyle is important. If you smoke now, quit smoking. Limit your alcohol intake.  Eat a balanced diet, with lots of green leafy vegetables and occasional fatty fish. Exercise and try to keep your weight within recommended limits.

More Information

Here are some questions you might ask your healthcare provider:

  • Do I have kidney cancer?
  • What is the stage and grade of my cancer and what does that mean?
  • Has the mass spread anywhere else? 
  • Is the mass likely to grow or spread some more?
  • Do I need other tests before we can decide on treatment?
  • What are my treatment choices? Which do you think I should choose, and why?
  • What should I expect after the procedure?
  • Will I have a lot of pain? How will my pain be managed?
  • Will I be cured after treatment?
  • What are the chances that the mass will return after treatment?
  • What risks or side effects should I expect from treatment? For how long?
  • What can I do to keep my kidneys functioning in a health manner?
  • What should I do to get myself ready for treatment? 
  • What will we do if the treatment doesn't work?
  • Can you recommend another urologist for a second opinion?
  • What more can I do to protect my health?
  • How often will I need to have checkups after treatment?
  • How long will I need to stay in the hospital?
  • Following surgery, will I need additional treatment?

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