Myxoid Liposarcoma

round cell liposarcoma, myxoid/round cell liposarcoma, MRCLS

Myxoid liposarcoma is a rare cancer that develops in fat cells, most commonly appearing as a slow-growing lump in the legs or arms. Many people carry this condition for years without noticing symptoms, as it typically grows quietly before becoming visible under the skin.

Table of contents

• What is myxoid liposarcoma?
• How common is myxoid liposarcoma?
• Symptoms and warning signs
• Causes and risk factors
• Diagnosis and testing
• Treatment options
• Outlook and follow-up care

What is myxoid liposarcoma?

Myxoid liposarcoma is a subtype of liposarcoma, a group of very rare cancers that begin in fat cells. The term “myxoid” comes from the gel-like, mucus-like substance called myxoid material that tumor cells produce, filling most of the tumor and giving it its distinctive appearance under a microscope^[1].

You can have this condition for several years before noticing symptoms, such as a visible lump under the skin on your legs or arms. Myxoid liposarcoma typically affects people ages 20 to 40, making it more common in younger adults compared to other types of liposarcoma^[1][3].

Most myxoid liposarcoma tumors grow very slowly and are not usually aggressive. However, some tumors combine myxoid cells with round cells, which get their name from the way they appear when examined under a microscope. When this combination occurs, healthcare providers use the term myxoid/round cell liposarcoma (MRCLS). These tumors with round cells tend to grow faster and behave more aggressively^[1][3].

Myxoid liposarcoma is most frequently found in the limbs, particularly the thighs. These tumors occur in the deep-seated areas between muscles or within fascial planes (layers of tissue that separate different muscle groups). They present as a large, slow-growing, painless mass^[4][8].

Myxoid/round cell liposarcoma tumors are more likely to spread from your arms and legs to nearby soft tissue, including muscle and skin. The cancer can also appear in your bones, such as your pelvic bones or spine, or organs, such as your heart, lungs or esophagus^[1].

How common is myxoid liposarcoma?

Myxoid liposarcomas are extremely rare. They account for 15% to 30% of all liposarcoma diagnoses. According to National Cancer Institute estimates, healthcare providers diagnose about 2,000 people in the U.S. with liposarcoma each year^[1][3].

In England, there are an average of 72 cases of myxoid liposarcoma diagnosed every year, making up around 16% of all liposarcoma diagnoses. Although myxoid liposarcoma can affect anyone of any age, the median age at diagnosis is 46 years old. The condition tends to affect more males than females^[4].

It is more common in people aged 20 to 40 years old and is rarely seen in children under 10 years old^[3].

Symptoms and warning signs

You can have myxoid liposarcoma without noticing any changes in your body. Many people with this condition do not have symptoms when the cancer first starts. Most people don’t notice changes until myxoid liposarcoma tumors grow large enough to create symptoms^[1][3].

The most common early sign is a visible lump in the affected area. This lump is usually painless but may cause discomfort if it presses on a nerve or nearby tissue. The lump often appears under the skin on your arms or legs, particularly the thigh^[1][6].

As the tumor grows larger, symptoms can include:

• A noticeable lump under your skin
• Pain or discomfort in the affected area
• Swelling or numbness in the area around the lump
• Weakness of the affected arm or leg
• Tiredness (fatigue)
• Nausea
• Unintended or unexplained weight loss^[1][3][4]

Because the condition can develop slowly and may not cause pain initially, it’s easy to overlook. However, you should see your doctor if you notice any new or unusual lumps, especially if they persist or continue growing^[6].

Causes and risk factors

Medical researchers aren’t sure exactly what causes myxoid liposarcoma. However, they have discovered important information about the genetic changes involved in this condition^[1].

Most people with myxoid liposarcoma carry a genetic mutation that turns normal genes into oncogenes. Oncogenes may turn normal cells into cancerous cells that multiply and develop into tumors^[1].

In most cases of myxoid liposarcoma, a chromosome (the structures in your cells that contains your genes) breaks apart and gets put back together in the wrong way. This can cause cells to not function like they should^[3].

In nearly all cases, a gene called FUS joins with a gene called CHOP (also known as DDIT3). This happens in almost all cases, so it may be very important for how myxoid liposarcoma forms. This fusion is notated as t(12;16)(q13;p11). In up to 10% of cases, a different fusion occurs between the EWSR1 gene and CHOP gene, notated as t(12;22)(q13;12)^[3][8].

Myxoid liposarcoma is not known to run in families. However, certain genetic conditions may increase your risk of developing liposarcoma. Genetic conditions such as Li-Fraumeni syndrome and neurofibromatosis may increase your risk of getting liposarcoma^[3].

While researchers don’t know exactly what causes myxoid liposarcoma, studies show that people who have radiation therapy for cancer have an increased risk of developing any kind of sarcoma, including myxoid liposarcoma^[1].

Diagnosis and testing

If you have symptoms of myxoid liposarcoma, your doctor will begin their diagnosis by doing a physical examination and asking about your symptoms. They will look at and feel any lump to assess its characteristics^[1][4].

Several tests may be used to diagnose myxoid liposarcoma:

Imaging tests help doctors see inside your body and locate tumors. Your doctor will use imaging scans to look at where the tumor is and how big it is. They will also check for signs that the tumor has spread to other parts of the body^[3].

• Computed tomography (CT) scan: CT scans help providers locate tumors — including how close they are to major organs — and evaluate tumor size^[1].
• Magnetic resonance imaging (MRI): MRI scans help providers check on nearby nerves, blood vessels and muscles that a liposarcoma may affect^[1].

Biopsy is essential for confirming the diagnosis. To check if the tumor is myxoid liposarcoma, your doctor will do a biopsy, taking a small sample from the tumor with a needle. An expert, called a pathologist, will study cells from the sample under the microscope to see what kind of tumor it is^[3][4].

Molecular and genetic testing confirms whether a tumor is a myxoid liposarcoma. These tests can identify the characteristic gene fusions (FUS-CHOP or EWSR1-CHOP) that are present in this type of cancer^[1][3].

Treatment options

Treatment for each patient will be unique. You should go to an expert in liposarcoma treatment to decide the best approach for your tumor. Healthcare providers treat myxoid liposarcoma with surgery, chemotherapy and/or radiation therapy^[1][3].

Surgery is the main treatment used for myxoid liposarcoma and the most common and reliable option. Surgery is often used to remove the main tumor while trying to avoid removing any healthy tissue. A surgeon removes the tumor and surrounding healthy tissue, including microscopic tumor cells. The surgeon will aim to take out an area of normal tissue around the tumor; this is known as taking a margin. It allows any cancer cells that are not visible to the naked eye to be removed along with the tumor, which can reduce the risk of the cancer coming back^[1][3][4].

Radiation therapy can be used around the time of surgery. Providers often use radiation therapy to shrink a myxoid liposarcoma before doing surgery to remove the tumor. The radiation is used to shrink the tumor so it can be removed by surgery. Radiation therapy can also be used after surgery if there is concern that tumor cells remain after surgery, to reduce the risk of cancer coming back (recurring)^[1][3].

Myxoid liposarcoma responds well to radiotherapy, so it may be used in addition to surgery^[4].

Chemotherapy may be used for cases that are difficult to treat by surgery or when the cancer has spread. Healthcare providers may use chemotherapy to treat tumors that surgery can’t remove. Myxoid liposarcoma also responds well to chemotherapy^[1][3][4].

Outlook and follow-up care

The outlook for someone with myxoid liposarcoma depends on many factors. Every person is different, and prognosis (the estimate of how a disease will affect you in the long term) will depend on several things:

• Where the tumor is in your body
• If the cancer has spread to other parts of your body
• How much of the tumor was taken out during surgery
• Whether the tumor contains round cells, which may be an adverse sign^[3]

The 5-year survival rate for patients with myxoid liposarcoma that is small and has not spread to other parts of the body is over 80%^[3].

After treatment, you will have regular follow-up appointments for several years. You should receive a follow-up schedule from your specialist. Follow-up care is necessary to make sure the tumor does not grow back^[3][4].

The usual practice for follow-up will include:

• A chance to discuss symptoms
• An examination to look for any signs of the sarcoma returning. This may include an MRI or ultrasound if required after examination
• A chest x-ray to rule out any secondary cancers occurring in the lungs^[4]

Cancer can reappear in the same area after the treatment of a previous tumor; this is called a local recurrence. If the cancer does reappear, it is important to get treated as quickly as possible^[4].