Your kidneys are two fist-sized, bean-shaped organs located near your back on either side of your spine at waist level.
Responsible for filtering your blood, the kidneys:
- Remove toxins
- Balance mineral levels
- Filter out extra water, producing about two quarts of urine each day
As an endocrine organ, your kidneys excrete hormones that trigger the production of red blood cells, control your blood pressure and regulate the metabolism of calcium. They also produce vitamin D. If your kidneys aren’t functioning at all, a treatment called dialysis steps in to help filter your blood, though it’s possible to function well with only one kidney.
Sometimes, the cells in your kidneys begin to grow unchecked, forming a tumor that may be benign (harmless) or malignant (cancerous). There are several forms of renal (kidney) cancer, the most common of which 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 is a rare type of 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).
Causes
Changes to the DNA that makes up the genes inside each of your cells may result in cancer, including renal sarcoma. Usually, DNA mutations that contribute to cancer impair the functioning of your oncogenes (which are the genes responsible for cell division and life) and/or your tumor suppressor genes (which help to keep cell division in check).
Risk factors
Even if you have one or more risk factors of renal sarcoma, you’re not guaranteed to develop it. While it’s possible to make positive changes to your lifestyle, some risk factors, such as your family history, are out of your control.
The following factors are linked to increased risk of kidney cancer.
- Smoking: The chances of developing kidney cancer drop if you stop smoking, though it would take years to reach the risk level of someone who never smoked.
- Race: Black people are more likely than white people to develop kidney cancer.
- Age: Kidney cancer typically is diagnosed in older adults between 50 and 70 years of age.
- High blood pressure: Even if you’re taking medications to manage the condition, the risk is still increased.
- Obesity: Changes in certain hormones may result in RCC.
- Family history: If you have a close relative who has had kidney cancer, you’re at an increased risk.
- Gender: Men are two to three times more likely than women to develop kidney cancer.
- Workplace exposure: If you’ve been exposed to materials containing cadmium, you face a greater risk.
- Medications: Overuse of medications that contain aspirin, ibuprofen or acetaminophen is linked to a higher risk of developing kidney cancer.
- Kidney disease: If you’ve had chronic kidney disease and diminished kidney function, you may be at an increased risk.
- Dialysis: If you’ve been on long-term dialysis, you may be more likely to develop cancer.
- Hereditary risk factors: Certain genetic conditions may increase the risk of kidney cancer.
Additional risk factors have been identified for soft tissue sarcomas, including renal cell sarcoma.
- Radiation exposure: If you’ve undergone radiation therapy to treat another kind of cancer, you 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), a hereditary condition that causes tumors to form in your nerves
- Gardner syndrome, a genetic disease that causes polyps in the colon and tumors outside of the colon
- Li-Fraumeni syndrome, an inherited condition that causes a higher risk of breast cancer, leukemia, brain tumors and soft tissue sarcomas
- Retinoblastoma, eye cancer caused by inherited gene defects that can increase the risk of sarcoma
- Werner syndrome, a condition marked by early-onset cataracts and heart issues, as well as 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, as well as some soft tissue sarcomas
- Tuberous sclerosis, a condition causing genetic defects that result in issues with learning and seizures and in kidney issues, including the growth of tumors
Symptoms
Early on, kidney cancers such as renal sarcoma will likely not cause symptoms. But over time, as the tumor grows, you may experience the following:
- Blood in your urine
- Pain in your lower back, usually on one side
- Palpable mass on your lower back or side
- Unexplained weight loss or diminished appetite
- General fatigue
- Unexplained fever
- Low red blood cell levels (anemia)
Diagnosis
If cancer is suspected, your doctor may conduct a variety of medical tests based on your symptoms, age and health history. There are no tests to screen for sarcoma, and diagnosis is usually obtained by a doctor’s examination along with imaging tests.
- X-ray: Though not as common for diagnosing soft tissue sarcomas such as renal sarcoma, X-rays use radiation to take images of your kidneys and other structures.
- Ultrasound: This technique uses sound waves to take pictures of your organs as well as the spaces beneath your skin where lumps may be present, which may help your doctor make a diagnosis.
- Computed tomography (CT) scan: This scan provides 3D images of your 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 your body (which is absorbed by cancerous cells) and taking detailed images of your internal structures.
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.
Treatment
The most common treatment for renal sarcoma is surgery. If you experience a recurrence of renal sarcoma, which is common, you may need additional surgeries or chemotherapy.
