Desmoplastic Small Round Cell Tumour

Desmoplastic small round cell tumour is a very rare and aggressive type of cancer that typically develops in the abdomen and pelvis, most often affecting young males between the ages of 10 and 30.

Table of contents

• What is desmoplastic small round cell tumour?
• Who gets desmoplastic small round cell tumour?
• Signs and symptoms
• What causes desmoplastic small round cell tumour?
• How is it diagnosed?
• Treatment options
• What to expect after treatment

What is desmoplastic small round cell tumour?

Desmoplastic small round cell tumour, often shortened to DSRCT, is a rare type of soft tissue sarcoma. A soft tissue sarcoma is a cancer that forms in the connective tissues of the body, such as fat, muscles, tendons, blood vessels, and nerves^[1].

In DSRCT, fast-growing tumours develop in the peritoneum, which is the membrane that lines the inside of the abdomen and pelvis^[3]. The tumours often form on the tissue lining and can quickly spread to other nearby organs, including the bladder, colon, and liver^[2].

• Peritoneum (abdominal and pelvic lining)
• Abdomen
• Pelvis

Under a microscope, DSRCT cells appear round and are surrounded by a dense, fibrous tissue called desmoplastic stroma^[9]. This distinctive appearance, along with specific genetic markers, helps doctors identify this particular type of cancer.

Who gets desmoplastic small round cell tumour?

DSRCT is extremely rare. It affects about 1 in 1 billion people worldwide since researchers first identified it in 1989^[3]. Some reports suggest that only about 200 cases have been recorded since the cancer was first described^[1].

While anyone can develop DSRCT, it most commonly affects young white males between the ages of 10 and 30^[1]. The disease typically appears in males between ages 20 and 30^[3]. It is much more common in males than females, with about 90% of patients being male^[6].

Signs and symptoms

Many people with DSRCT do not have symptoms when the cancer first starts^[1]. You may not develop symptoms until tumours get large enough to affect your abdomen and digestive system^[3]. The tumour can grow to a large size and coat the inside surface of the abdomen before a person notices it^[6].

Later, when the tumours get larger, common symptoms include^[1][3]:

• Swelling in the abdomen (distended or swollen belly)
• Abdominal pain
• Nausea and vomiting
• Constipation
• Diarrhea
• Difficulty urinating
• Unexplained weight loss

The main symptom of DSRCT is often a solid mass or painful lump in the abdomen or belly button area^[6]. Many of these symptoms, like constipation, diarrhea, nausea, and vomiting, are common and can happen for many different reasons. However, you should consider talking to a healthcare provider if you have symptoms like these that get worse or last for more than a few days^[3].

In more than 40% of patients, the cancer can spread to the liver, lymph nodes, lungs, bones, and other parts of the body^[6]. In late stages, patients may develop pleural effusions, pleural implants, or mediastinal adenopathy^[9].

What causes desmoplastic small round cell tumour?

It is not clear what causes desmoplastic small round cell tumours^[2]. Researchers know this condition happens when changes in certain chromosomes (the structures in your cells that contain all of your genes) create an abnormal gene. However, they do not know what triggers the change^[3].

In DSRCT, chromosomes break apart and get put back together in the wrong way^[1]. A gene called EWS (Ewing sarcoma gene) wrongly joins with a region called WT1 (Wilms tumour gene). This creates a fusion gene known as EWS-WT1^[1][10]. The specific chromosomal change is expressed as t(11:22)(p13:q12)^[10].

This fusion gene acts as an oncogenic transcription factor, meaning it influences the expression of various proteins that can lead to cancer development^[10]. Doctors will look for this change in chromosomes to confirm that your cancer is DSRCT^[1].

Because there are so few people with DSRCT, we do not know if it runs in families^[1].

How is it diagnosed?

Healthcare providers diagnose DSRCT through a combination of physical examination, imaging tests, and laboratory tests^[3][6].

Physical examination

Your doctor will perform a physical examination to check for masses or lumps in your belly^[3].

Imaging tests

If you have symptoms of DSRCT, your doctor will use imaging scans to look at where the tumours are and how big they are. They will also check for signs that the tumour has spread to other parts of the body^[1]. Imaging tests may include^[1][3][6]:

• CT scans (computed tomography scans)
• MRI scans (magnetic resonance imaging)
• Ultrasound
• PET scans (positron emission tomography)

Biopsy

To check if the tumour is DSRCT, your doctor will do a biopsy, taking a small sample from the tumour with a needle or during a surgical procedure^[1][6]. An expert called a pathologist will study cells from the sample under the microscope to see what kind of tumour it is^[1].

Under a microscope, DSRCT cells look round^[1]. The pathologist might also check for a protein called EWS-WT1 that this type of tumour makes^[1].

Genetic tests

Genetic tests look for the chromosomal change that causes DSRCT^[3]. The confirmation of the EWS-WT1 translocation by biopsy is now an essential part of the workup and is required to definitively establish the diagnosis of DSRCT^[9].

Treatment options

There is currently no standard of care for DSRCT because it is so rare^[1]. However, treatment typically involves a combination of treatments^[2]. Most people with this cancer receive multiple types of treatment^[3].

Chemotherapy

Chemotherapy uses anti-cancer drugs to destroy cancer cells^[8]. When the tumours are large, or the cancer cells have spread to other parts of the body, chemotherapy is used along with surgery^[1]. Doctors may also use chemotherapy before surgery to shrink the tumour, making it easier to remove^[8].

Surgery

Surgery is used to remove as much of the DSRCT as possible^[1]. The goal of surgery is to remove all of the cancer, though it might not be possible if the cancer has grown into nearby organs^[20]. Because these tumours grow in and around other organs, it is usually not possible to remove the entire tumour^[6].

If some cancer cells are left behind, the cancer can come back in the same spot or a different part of the body^[1]. When it is not possible to remove the cancer entirely, your surgeon may work to remove as much as possible^[20].

HIPEC (Hyperthermic Intraperitoneal Chemotherapy)

HIPEC is a specialized treatment that washes the inside of the abdomen with warm chemotherapy drugs^[1]. This procedure lasts about two hours and can be done along with surgery^[1]. Healthcare providers may treat desmoplastic small round cell tumours with HIPEC, which involves circulating heated chemotherapy drugs in your abdominal cavity after surgery^[3].

The chemotherapy kills the tumour cells in the abdomen without exposing the rest of the body to the drugs, which can cause side effects^[1].

Radiation therapy

Radiation therapy uses radiation to kill cancer cells^[1]. You may have radiotherapy either before or after surgery^[8]. External radiation therapy comes from a machine that aims radiation at the tumours. For internal radiation therapy, seeds, ribbons, or capsules that contain a radiation source are placed in your body, in or near the tumour^[1].

Before surgery, radiotherapy aims to shrink the tumour, making it easier to remove. After surgery, radiotherapy aims to kill any cancer cells that surgery did not remove^[8]. Proton therapy is a type of radiation therapy that targets the tumour while avoiding organs and healthy tissue, meaning fewer short-term and long-term side effects from radiation^[6].

Treatment side effects

Surgery, chemotherapy, and radiation therapy cause different side effects^[3]. Surgery to remove DSRCTs may cause side effects that include a reaction to general anesthesia and bleeding. Common radiation and chemotherapy side effects are^[3]:

• Diarrhea
• Fatigue
• Nausea and vomiting

Palliative care

Regardless of treatment type, ask your healthcare team about palliative care. In palliative care, you receive medical, social, and emotional support that may help you to cope with living with a serious illness^[3].

What to expect after treatment

Treatment may put the condition into remission, meaning you do not have symptoms and tests do not find signs of disease. However, remission often does not last, and you will probably need new or different treatment for recurring tumours^[3]. Healthcare providers have treatments that can put the condition into remission, but it often comes back (recurs)^[3].

Your prognosis is what healthcare providers believe you can expect to happen after treatment. They base prognoses on information like tumour locations, whether tumours spread, and how much of the tumour they were able to remove during surgery^[3].

Because these are very rare tumours, there is not a lot of research that providers can evaluate to develop a prognosis. That makes it hard for them to say what you can expect, including how long you may live^[3]. Prognosis for this disease is quite poor, with five-year overall survival estimated at only 15 to 30%^[9]. Right now, most survival rate data show between 15% and 38% of people with DSRCT were alive five years after diagnosis^[3].

After treatment, you will need follow-up care to check for recurrence and to deal with any side effects of the disease or its treatment^[22]. Life as a cancer survivor will include regular visits with your cancer care team to ensure the best possible outcomes and to help prevent or treat any complications following treatment^[22].