Renal sarcoma

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on May 20, 2022.

Renal sarcoma is a rare type of kidney cancer that forms in the kidney’s soft tissue, the connective tissue that surrounds the kidneys or the fat around the kidneys. Fewer than 1 percent of kidney cancers are renal sarcomas, according to the American Cancer Society (ACS).

Renal sarcoma causes

Changes to the DNA that makes up the genes inside each of the cells may result in cancer, including renal sarcoma. Usually, DNA mutations that contribute to cancer impair the functioning of oncogenes (which are the genes responsible for cell division and life) and/or tumor suppressor genes (which help to keep cell division in check).

The kidneys are two fist-sized, bean-shaped organs located near the back on either side of the spine at waist level.

Responsible for filtering blood, the kidneys:

  • Remove toxins
  • Balance mineral levels
  • Filter out extra water, producing about two quarts of urine each day

As an endocrine organ, the kidneys excrete hormones that trigger the production of red blood cells, control blood pressure and regulate the metabolism of calcium. They also produce vitamin D. If the kidneys aren’t functioning at all, a treatment called dialysis steps in to help filter the blood, though it’s possible to function well with only one kidney.

Sometimes, the cells in the kidneys begin to grow unchecked, forming a tumor that may be benign (harmless) or malignant (cancerous). Of the several forms of renal (kidney) cancer, the most common is renal cell carcinoma (RCC), which makes up about 85 percent of all kidney cancer cases in adults, according to the American Society of Clinical Oncology (ASCO).

Renal sarcoma risk factors

Even if someone has one or more risk factors of renal sarcoma, he or she isn't guaranteed to develop it. While it’s possible to make positive lifestyle changes, some risk factors, such as family history, are out of a person's control.

The following factors are linked to increased risk of renal sarcoma.

Smoking: The chances of developing renal sarcoma drop after quitting smoking, though it would take years to reach the risk level of someone who never smoked.

Age: Renal sarcoma typically is diagnosed in older adults between 50 and 70 years of age. 

Obesity: Being obese may be a risk factor for developing renal sarcoma.

Family history: If the patient has a close relative who has had kidney cancer, it may lead to an increased risk for developing the disease.

Chemical exposure: People who have been exposed to materials containing cadmium, asbestos, some metals and certain herbicides face a greater risk.

Kidney disease: If someone has had chronic kidney disease and diminished kidney function, he or she may be at an increased risk.

Dialysis: If someone has been on long-term dialysis, he or she may be more likely to develop renal sarcoma.

Hereditary risk factors: Certain genetic conditions may increase the risk for developing renal sarcoma, such as Von Hippel-Lindau (VHL) syndrome.

Additional risk factors have been identified for soft tissue sarcomas, including renal cell sarcoma, which are listed below.

Radiation exposure: If a patient has undergone radiation therapy to treat another kind of cancer, he or she may be at slightly increased risk of developing a sarcoma.

Family cancer syndromes: Several disorders caused by inherited genetic mutations are known to increase the risk of sarcoma.

Neurofibromatosis (von Recklinghausen disease): This hereditary condition may cause tumors to form in the nerves.

Gardner syndrome: A genetic disease that causes polyps in the colon and tumors outside of the colon.

Li-Fraumeni syndrome: This inherited condition may lead to a higher risk of breast cancer, leukemia, brain tumors and soft tissue sarcomas

Retinoblastoma: Eye cancer caused by inherited gene defects may increase the risk of sarcoma.

Werner syndrome: A condition marked by early-onset cataracts and heart issues, this syndrome may lead to an increased risk of soft tissue sarcomas and other cancers.

Gorlin syndrome (nevoid basal cell carcinoma syndrome, NBCCS): A condition associated with a high risk of basal skin cell carcinoma, this condition may increase the risk for developing some soft tissue sarcomas.

Tuberous sclerosis: A condition causing genetic defects, this disease may result in issues with learning and seizures and in kidney issues, including the growth of tumors.

Renal sarcoma symptoms

Early on, kidney cancers such as renal sarcoma may not cause symptoms. But over time, as the tumor grows, the patient may experience one or more of the symptoms listed below.

  • Blood in the urine
  • Pain in the lower back, usually on one side
  • Palpable mass on the lower back or side
  • Unexplained weight loss or diminished appetite
  • General fatigue
  • Unexplained fever
  • Low red blood cell levels (anemia)
  • High blood pressure (hypertension)
  • anemia (reduced red blood cell count)

Renal sarcoma diagnosis and detection

If cancer is suspected, the care team may conduct a variety of medical tests based on the patient's symptoms, age and health history. No tests are available to screen for renal sarcoma, and diagnosis is usually obtained by a doctor’s examination along with imaging tests.

The care team may perform one or more of the tests listed below during the renal sarcoma diagnosis process.

X-ray: Though not commonly used for diagnosing soft tissue sarcomas such as renal sarcoma, X-rays use radiation to take images of the kidneys and other structures.

Ultrasound: This technique uses sound waves to take pictures of the organs as well as the spaces beneath the skin where lumps may be present, which may help the care team make a diagnosis.

Computed tomography (CT) scan: This scan provides 3D images of the organs to help ascertain the size and location of a tumor.

Magnetic resonance imaging (MRI) scan: Magnetic energy is used to obtain images and determine the size of a tumor.

Positron emission tomography (PET) scan: Typically used along with a CT scan, this procedure involves injecting a radioactive sugar substance into the body (which is absorbed by cancerous cells) and taking detailed images of the internal structures.

Urinalysis: The care team may order a urinalysis or other lab tests to evaluate whether the patient's kidney function is within normal limits.

If a tumor is present, a kidney biopsy, or small tissue sample, is taken to be evaluated with a microscope by a pathologist. Because renal sarcoma is so rare, an expert should be consulted to ensure accurate diagnosis.

Renal sarcoma treatment

The most common treatment for renal sarcoma is surgery. If the patient experiences a cancer recurrence following treatment, which is common, he or she may need additional surgeries or chemotherapy.

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