What Is Sarcomatoid Renal Cell Carcinoma?

A Rare Type of Kidney Cancer

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Sarcomatoid renal cell carcinoma is an uncommon kind of kidney cancer. People who have it tend to do worse than those with some other kinds of kidney cancer. 

The word “sarcomatoid” comes from the shape and appearance of these cells. When examined under the microscope, they tend to have a circular middle that tapers out at the ends. Scientists first described the disease in the 1960s.

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Types

Sarcomatoid renal cell carcinoma falls into a broader group of kidney cancers called renal cell carcinoma (RCC). “Renal” means “kidney.” “Carcinoma” is a word for cancers that begin in cells lining the internal organs. About 90% of cancers that begin in the kidney are classified as renal cell carcinoma.

Through research, scientists eventually learned that certain kidney cancers behave somewhat differently than other renal cancers. That is, if someone’s cancer cells looked a certain way under a microscope, they classified them into different categories. And those cancers seemed to share certain similarities, like how well they respond to certain treatments.

The most common types of RCC include:

  • Clear cell
  • Papillary
  • Chromophobe
  • Clear cell papillary
  • Collecting duct
  • Medullary
  • Unclassified

These different categories can get very confusing and, therefore, are differentiated by their appearances. For example, clear cell renal cell carcinoma, the most common subtype of renal cell carcinoma, is named for the way that its cells look under the microscope when stained with certain dyes. 

What Type Is Sarcomatoid RCC?

Sarcomatoid RCC isn’t technically considered a specific subtype of RCC. Rather, people will usually have one of the subtypes (like clear cell carcinoma) along with sarcomatoid RCC.

For those people, many of their cells look like a subtype of RCC (such as clear cell carcinoma). However, they also have some cancer cells that have a different appearance (called sarcomatoid). This is also sometimes called having sarcomatoid features. 

In most of the subtypes of RCC, these sarcomatoid features can be found in some people. Much less commonly, some people have sarcomatoid RCC only, and no other classification applies.

Roughly 4%–5% of people with renal cell carcinoma have sarcomatoid RCC. Unfortunately, about 60%–80% of people with sarcomatoid RCC have advanced disease when they are first diagnosed.

Symptoms of Sarcomatoid Renal Cell Carcinoma

Most people with sarcomatoid renal cell carcinoma have symptoms when they are first diagnosed. Symptoms can vary based on how much the cancer has spread and other factors. Some potential symptoms include:

  • Pain in your back, upper belly, or side (sometimes called “flank pain”)
  • Blood in your urine
  • Bone pain
  • Weight loss
  • Fever
  • Cough or shortness of breath
  • Fatigue

However, some people diagnosed with sarcomatoid RCC won’t have any symptoms when they are diagnosed. 

Causes

Scientists are still learning about what causes sarcomatoid renal cell carcinoma. A lot of complex genetic and environmental factors seem to be involved.

Like other kinds of cancer, sarcomatoid RCC develops partly due to changes in a person’s genetic material. Many factors can make your genetic material—your DNA—to become slightly damaged during your lifetime. That’s called an acquired genetic mutation.

Usually, this isn’t a big deal. However, if a specific cell inside your kidneys gets several mutations (changes), it might start to behave abnormally. For example, it might start to grow and reproduce when it normally shouldn’t. Such a cell is said to have become cancerous. 

What Factors Increase Risk?

Certain factors can accelerate the formation of dangerous mutations, increasing your risk of of renal cell carcinoma, including:

  • Smoking
  • High blood pressure
  • Other kinds of kidney disease
  • Exposure to certain toxins

People in certain jobs are more likely to be exposed to these toxins, too, such as mechanics or people who work in dry cleaning. However, most of the time, a clear cause can’t be found.

Researchers are still learning a lot about the specific genes that might be damaged in sarcomatoid RCC.  

Diagnosis

To diagnose this disease, first, the doctor takes your medical history, asking you about current symptoms and your other medical conditions. That, paired with a physical exam, may point to kidney cancer as a potential concern.

Medical Tests

Although they can’t be used for direct diagnosis, a number of medical tests can provide some clues into your condition. They might also rule out other potential causes of your symptoms. Some of these might include:

  • Analysis of a urine sample (urinalysis, to look for blood and other characteristics)
  • Creatinine (to check for kidney function)
  • Alkaline phosphatase (to give clues about potential spread to the bones)

Imaging Tests

Certain imaging tests can also be important for diagnosis. These can often reveal if something abnormal is present in the kidney. For example, these might include one or more of the following:

When combined, these tests can give doctors a very good idea of whether a person has some type of kidney cancer. However, for a definitive diagnosis, a specialist known as a pathologist must examine a sample of the affected area under a microscope.

This can happen in different ways. Much of the time, the clinician can tell from all these other indicators that a kidney cancer is very likely. If so, they might plan to go ahead with surgical removal of the area. Surgical removal is often a partial nephrectomy, which is the removal of the cancer along with some surrounding kidney tissue. The adrenal gland, nearby lymph nodes, and some fatty tissue around the kidney may also be removed.

After that happens, they can send a portion of the affected area to the laboratory. The pathologist then examines the cells and determines if cancer is present and what type it is. 

After your lab results come back, you might be told that you have renal cell carcinoma. The lab report will also have specific information about the nature of your cancer. For example, you might be told you have a specific subtype of RCC (like clear cell RCC) with sarcomatoid features. 

Biopsy

In other cases, a person might have a kidney biopsy before surgery, if it’s not clear yet that cancer is really the problem. In this case, a tissue sample is also removed and sent to the laboratory. There, an expert looks under the microscope to definitively diagnose sarcomatoid RCC.

Treatment

Treatment for sarcomatoid renal cell carcinoma will depend on the cancer’s stage. This refers to the size of the tumor and whether the cancer has spread throughout your body. 

Surgery

If your cancer hasn’t spread through the body (called metastasis), surgery is likely to be the main approach. Your surgeon might recommend total removal of your kidney (radical nephrectomy). 

For some people this surgery can completely cure the disease. However, this is less effective in sarcomatoid RCC than in some other kidney cancer types. In about 80% of people, the cancer will come back within a couple of years, even if your surgeon tries to remove all of it.

If your doctors go for this approach, you might not need any further treatment. However, your doctor will probably want to monitor your kidneys for signs that your cancer has returned. For example, you might need periodic imaging tests, such as CT scans.

In people with more advanced disease, their cancer has already spread more extensively throughout their body. Surgery alone can’t cure the disease.

However, surgery is still sometimes helpful, such as to relieve symptoms in the short term, even though it won’t cure your disease.

Scientists aren’t in total agreement about the best approach to treat sarcomatoid RCC that is more advanced. A lot of treatments might be used that, unfortunately, tend not to work as well as they often do for other kinds of RCC. 

Medications

A group of drugs called angiogenesis inhibitors may be tried. These block the tumor's ability to form new blood vessels that, in turn, slows tumor growth. Some of these are:

  • Sutent (sunitinib)
  • Votrient (pazopanib)
  • Cometriq (cabozantinib)
  • Zortress (everolimus)

Another option is a group of drugs called checkpoint inhibitors. Scientists are very hopeful about the potential of these new drugs. Ones sometimes used are:

  • Keytruda (pembrolizumab)
  • Avastin (bevacizumab)

Radiotherapy

Another approach sometimes used is radiotherapy, or radiation therapy. This tends to not be very successful, but it might reduce the size of the tumor and temporarily relieve symptoms. 

Chemotherapy

Doctors have also tried chemotherapy as treatment. But it too isn't very effective. Some possible approaches are:

Your doctor may also combine one or more of these therapies, like prescribing an angiogenesis inhibitor drug with a checkpoint inhibitor drug. You also might need to switch therapies if one choice doesn’t seem to be working.

Scientists are actively seeking better options to treat sarcomatoid RCC.

Prognosis

Unfortunately, being told that you have sarcomatoid RCC is not good news. People with sarcomatoid RCC tend to not fare well. This is partly because they tend to be diagnosed at later stages than some other kinds of RCC. It is also partly because they don’t respond as well to therapy as people with some other kinds of cancer.

On average, people treated for sarcomatoid RCC tend to live for an average of 5–12 months after their diagnosis.

Summary

Sarcomatoid RCC is a rare kind of kidney cancer. A person can have it in addition to an official subtype of RCC, such as clear cell RCC. This cancer is hard to treat and often isn’t diagnosed until after the cancer has spread. 

A Word From Verywell

Receiving any kind of cancer diagnosis is devastating. If you’ve learned that your renal cell carcinoma has sarcomatoid features, you may be even more disheartened. Lean on your family, your friends, and on your medical team. By getting all your questions answered fully, you’ll feel better about your medical decisions. 

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