What if your cancer looked like two cancers in one? That’s the case with sarcomatoid renal cell carcinoma (RCC), sometimes called SRCC. SRCC isn’t its own type of cancer. It happens when RCC cells start to look and act more like sarcoma, a fast-growing soft tissue cancer. This change makes the cancer harder to treat and more likely to spread.

Most people have never heard of SRCC. That’s because it’s rare. However, for people with this RCC diagnosis and their loved ones, it’s important to understand what makes this type of kidney cancer different. This article explains what defines SRCC, what symptoms to watch for, how it’s treated, and what questions to ask your doctor.

1. Sarcomatoid RCC Is a Rare and Aggressive Form of Kidney Cancer

SRCC happens when regular kidney cancer cells begin to change and take on sarcomatoid features. This means the cells look more like those found in sarcoma — a type of cancer that affects bones and soft tissues. This change is also called sarcomatoid differentiation. These changes are often a sign that the tumor is high grade, which means it grows and spreads faster than other kidney cancers.

SRCC is extremely rare. In the U.S., around 81,000 people are diagnosed with kidney cancer every year. Of those, about 80 percent to 85 percent have RCC. Only about 5 percent of those RCC cases show sarcomatoid features. That means that fewer than 4,000 people in the U.S. are diagnosed with SRCC each year.

Because so few people have this type of cancer, there aren’t as many clinical trials or research studies focused on it. Most of the information we have about SRCC comes from retrospective reviews, where doctors look back at past cases. Researchers are still actively studying it, and there may be clinical trials you qualify for. If you’re interested in taking part, reach out to your healthcare team or visit clinicaltrials.gov.

2. Sarcomatoid RCC Can Develop From Different RCC Types

SRCC can appear in any of the main types of RCC. It’s more common in clear cell RCC but can also show up in non-clear types. The non-clear subtypes of RCC include papillary, chromophobe, collecting duct, and translocation carcinomas.

When doctors look at the tumors under a microscope, they may see sarcomatoid features. These features make the cancer cells look long, thin, and stretched out, like spindles. That’s why one type of SRCC is called spindle-cell carcinoma.

In other types, the cells may also look jumbled and disorganized under the microscope. This pattern is very different from the more round and uniform appearance of regular kidney cells. Some sarcomatoid tumors also contain pleomorphic cells. This means the cancer cells are all different shapes and sizes, a subtype called pleomorphic carcinoma.

3. Researchers Don’t Know Why Some People Get Sarcomatoid RCC

There are no known, specific causes of SRCC. It’s not hereditary, meaning it doesn’t usually run in families. However, certain inherited conditions — like von Hippel-Lindau disease, Birt-Hogg-Dubé syndrome, and hereditary papillary RCC — raise the risk of RCC in general. It’s still unclear whether these hereditary conditions raise the risk of developing SRCC.

According to the American Cancer Society, men are twice as likely to develop RCC as women. Other risk factors that have been linked to the overall risk of RCC include:

• Smoking or tobacco use
• High blood pressure
• Obesity
• Chronic kidney disease
• Older age (usually over 60)
• Exposure to certain workplace chemicals

Sometimes, SRCC can form in people with kidney cancer risk factors. But it doesn’t happen often, and doctors don’t fully understand why. Scientists are still trying to learn more by studying changes in genes and cell signals in the body.

4. Sarcomatoid RCC Often Appears at a More Advanced Stage

SRCC is more aggressive than other types of kidney cancer. That means it tends to grow faster and spread earlier, even if the original tumor in the kidney is still small. In many cases, SRCC is already advanced or metastatic (has spread to other body parts) by the time it’s diagnosed.

Tumors with sarcomatoid features often grow in a disorganized way and invade nearby tissues more quickly. These tumors also have a higher chance of showing tumor necrosis. This means parts of the tumor die due to rapid, uncontrolled growth.

Whenever RCC shows sarcomatoid components, it is automatically classified as grade 4 — the highest (most abnormal-looking) grade for kidney cancer.

5. Symptoms of Sarcomatoid RCC May Be Subtle at First

Symptoms of SRCC may not be obvious. Like other types of kidney cancer, many tumors are found by accident during tests for other health issues. When symptoms do appear, they’re usually similar to those seen in other kidney cancers and are not unique to SRCC.

Common symptoms might include:

• Pain in the lower back on one side, not caused by an injury
• Blood in the urine
• Unintended or unexplained weight loss
• A mass (lump) in the belly or lower back
• Fatigue (extreme tiredness)
• Fever that isn’t caused by another illness or infection
• Swelling of the scrotum or varicocele (veins in the scrotum)

Since SRCC is more aggressive, these symptoms may show up sooner or be more severe once the cancer starts to spread. Still, many people show no symptoms until the disease is advanced.

6. Treating Sarcomatoid RCC Often Requires Multiple Approaches

Because SRCC is aggressive, treatment may require a combination of strategies. The goal is to control the cancer, relieve symptoms, and improve quality of life.

If the cancer is still in the kidney and hasn’t spread far, doctors may recommend surgery to remove the entire kidney that has the tumor. This is called a radical nephrectomy. In some cases where the cancer has already spread (called metastatic disease), doctors may still perform surgery, known as a cytoreductive nephrectomy, to remove as much of the cancer as possible while preserving kidney function.

Most people will also need systemic therapy, which treats the whole body. This includes immunotherapy, targeted therapy, or both.

Immunotherapy helps your immune system recognize and attack cancer cells. Checkpoint inhibitors, such as drugs that block programmed cell death ligand 1 (PD-L1) or programmed cell death protein 1 (PD-1), are common choices. These treatments are especially helpful for SRCC because tumors with sarcomatoid features often express high levels of PD-L1, making them more likely to respond.

Targeted therapy works differently. It blocks specific proteins, like vascular endothelial growth factor (VEGF), that tumors need to grow new blood vessels and spread. These drugs slow down cancer growth and may shrink tumors over time.

7. Prognosis Can Be Challenging, but It Varies

SRCC is linked to a poor prognosis (outlook), especially when diagnosed at a later stage. Since it grows and spreads so quickly, many people are already facing metastases by the time they’re diagnosed. This makes treatment harder and reduces the chance of long-term survival.

Studies show that the median survival (about half of people with a certain condition) for people with metastatic SRCC is typically less than one year. This means that about half of the people with metastatic SRCC live one year beyond their diagnosis date.

However, this can vary. Some people respond well to surgery and systemic therapy, which can increase lifespan. Other factors that can affect survival outcomes include:

• The amount of cancer that has sarcomatoid features
• Tumor size and stage, and whether cancer has spread to lymph nodes or other organs
• The presence and extent of tumor necrosis
• The type of RCC you have (such as clear cell, papillary, or chromophobe)
• Your overall health and response to treatment

Even with a less favorable outlook, it’s important to remember that responses to SRCC treatment vary. Some people can improve, especially with newer therapies. Regular follow-up with your oncology (cancer) team can help ensure access to every available treatment option. They can also provide advice and support on how to improve your quality of life while living with SRCC.

Talk With Others Who Understand

On MyKidneyCancerTeam, people with kidney cancer and their loved ones come together to ask questions, give advice, and share their stories with others who understand life with kidney cancer.

Have you been diagnosed with sarcomatoid renal cell carcinoma? What tests led to your diagnosis? Share your story in the comments below, or start a conversation by posting on your Activities page.