Myxoid liposarcoma is a rare type of cancer that develops in fat cells, most commonly appearing as a painless lump in the thigh or other parts of the arms and legs. This condition often grows slowly over several years before symptoms become noticeable, typically affecting adults between the ages of 20 and 40. Understanding this uncommon cancer can help patients and their families navigate diagnosis and treatment options.
How Common Is Myxoid Liposarcoma?
Myxoid liposarcoma is an extremely rare form of cancer. Healthcare providers diagnose approximately 2,000 people in the United States with liposarcoma—a cancer that grows in the cells that store fat in the body—each year. Among all liposarcoma cases, myxoid liposarcoma accounts for between 15% and 30% of diagnoses, making it one of the more common subtypes of this already rare cancer.[1][3]
According to data from England, there are an average of 72 cases of myxoid liposarcoma diagnosed every year, representing around 16% of all liposarcoma diagnoses in that country. The disease typically affects adults, with the median age at diagnosis being 46 years old. Myxoid liposarcoma is more commonly diagnosed in males than females, and it is rarely seen in children under 10 years old.[4][3]
The condition predominantly affects people aged 20 to 40 years old, setting it apart from many other cancers that tend to occur later in life. This younger age range makes myxoid liposarcoma particularly significant, as it can impact individuals during their most productive years.[1]
What Causes Myxoid Liposarcoma?
Medical researchers have not yet determined the exact cause of myxoid liposarcoma. However, they have identified important genetic changes that appear to play a central role in how this cancer develops. Most people with myxoid liposarcoma carry a genetic mutation—a change in the DNA sequence of their cells—that transforms normal genes into oncogenes. Oncogenes are altered genes that can cause normal cells to become cancerous, multiply uncontrollably, and eventually develop into tumors.[1]
In the vast majority of myxoid liposarcoma cases, scientists have observed a specific genetic error called a chromosomal translocation. This occurs when a chromosome—the structure in your cells that contains your genes—breaks apart and gets reassembled in the wrong way. When chromosomes are incorrectly put back together, the cells containing them may not function as they should.[3]
In myxoid liposarcoma, a gene called FUS (also part of the FET gene family) joins with a gene called CHOP (also known as DDIT3). This fusion happens in almost all cases of myxoid liposarcoma, suggesting it may be critically important for how this cancer forms. The FUS-DDIT3 fusion gene forms through a merger of part of the FUS gene normally located on chromosome 16 with part of the DDIT3 gene normally located on chromosome 12. Laboratory studies suggest that this fusion gene may act as an oncogene to promote the development of myxoid liposarcoma. In a smaller number of cases—up to 10%—a similar fusion occurs between the EWSR1 gene and the DDIT3 gene.[3][8]
Scientists are working to understand exactly how these genetic fusions cause cancer cells to develop and grow. Understanding these mechanisms may eventually lead to the development of new, targeted therapies specifically designed to combat myxoid liposarcoma.[3]
Risk Factors for Developing Myxoid Liposarcoma
While the exact cause of myxoid liposarcoma remains unclear, researchers have identified certain factors that may increase a person’s risk of developing this cancer. One known risk factor is previous exposure to radiation therapy—treatment that uses high-energy radiation to kill cancer cells. Studies have shown that people who have received radiation therapy for another cancer have an increased risk of developing any kind of sarcoma, including myxoid liposarcoma, later in life.[1]
Certain inherited genetic conditions may also increase the risk of developing liposarcoma. People with Li-Fraumeni syndrome—a rare inherited disorder that dramatically increases the risk of developing several types of cancer, often at an early age—have a higher likelihood of developing liposarcoma. Similarly, individuals with neurofibromatosis—a genetic disorder that causes tumors to form on nerve tissue—may also face an increased risk of liposarcoma.[3]
However, it is important to note that myxoid liposarcoma itself is not known to run in families. Having a family member with myxoid liposarcoma does not automatically increase your risk unless an underlying genetic syndrome like those mentioned above is present.[3]
Recognizing the Symptoms
One of the challenging aspects of myxoid liposarcoma is that many people do not experience any symptoms when the cancer first develops. The disease can be present for several years before it becomes noticeable. Most people only become aware of a problem when the tumor grows large enough to create visible or physical changes in the body.[1]
The most common symptom of myxoid liposarcoma is a noticeable lump under the skin. This lump typically appears on the legs—especially the thigh—or arms. The lump may feel soft or firm to the touch and is often painless in the early stages. Because these tumors can grow slowly over many years, people may mistake them for harmless fatty lumps or lipomas, which are benign and far more common than liposarcomas.[3]
As the tumor continues to grow, additional symptoms may develop. Pain can occur if the tumor presses against nearby nerves or tissues. Some people experience tiredness or fatigue—a persistent feeling of exhaustion that does not improve with rest. Nausea and unintended or unexplained weight loss may also occur, particularly if the cancer is more advanced.[1]
When myxoid liposarcoma develops in the limbs, it can cause specific localized symptoms. A persistently growing lump, swelling or numbness in the area around the lump, and weakness of the affected arm or leg are all potential signs. If the tumor is located in the torso or abdominal area, symptoms might include stomach pain or cramping and a gradually increasing size of the abdomen.[4]
Because the early symptoms can be subtle or absent, many cases of myxoid liposarcoma are not diagnosed until the tumor has grown significantly. This is why any new lump that persists or continues to grow should be evaluated by a healthcare provider, even if it is not causing pain or other obvious problems.[5]
Understanding the Different Forms
Not all myxoid liposarcomas behave in the same way. Healthcare providers recognize that myxoid liposarcoma can be divided into different subtypes based on the appearance of the cells under a microscope and how aggressively the cancer behaves. Understanding these subtypes is important because they can affect treatment decisions and outcomes.[1]
Most myxoid liposarcoma tumors grow very slowly and are not considered aggressive cancers. These are sometimes called low-grade or pure myxoid liposarcomas. However, some myxoid liposarcoma tumors contain a mixture of myxoid liposarcoma cells and another type of cell called round cells. Round cells get their name from their circular appearance when viewed under a microscope by a pathologist—a doctor who specializes in diagnosing diseases by examining tissues and cells.[1]
When a tumor contains a significant number of round cells, healthcare providers may use the term myxoid/round cell liposarcoma (MRCLS). The presence of round cells—particularly when they make up more than 5% of the tumor—is associated with more aggressive behavior. Tumors with a high percentage of round cells are more likely to metastasize, meaning they can spread from the original site in the arms or legs to nearby soft tissue, including muscle and skin. These tumors can also spread to bones, such as the pelvic bones or spine, or to organs such as the heart, lungs, or esophagus.[1][3]
The percentage of round cells in the tumor is strongly associated with patient outcomes. Tumors with a higher round cell component tend to have a higher incidence of distant metastasis and a poorer prognosis overall. This is why accurate identification of the tumor subtype through careful pathological examination is so important for planning treatment and predicting outcomes.[10]
How Doctors Diagnose Myxoid Liposarcoma
Diagnosing myxoid liposarcoma involves several steps, starting with a physical examination. When a patient notices a lump or other concerning symptom and visits their doctor, the provider will begin by examining the area and asking questions about when the lump appeared, whether it has changed, and what other symptoms are present.[1]
If myxoid liposarcoma is suspected, the next step typically involves imaging tests. A computed tomography (CT) scan uses X-rays taken from different angles and computer processing to create detailed cross-sectional images of the body. CT scans help providers locate tumors, determine how close they are to major organs, and evaluate tumor size. Magnetic resonance imaging (MRI) uses powerful magnets and radio waves to create detailed pictures of the inside of the body. MRI scans are particularly useful for checking on nearby nerves, blood vessels, and muscles that a liposarcoma may affect.[1]
Imaging tests can show the location and size of a tumor, but they cannot definitively determine whether the tumor is cancerous or what specific type of cancer it might be. To make a definitive diagnosis, doctors need to examine the actual tumor cells. This is done through a biopsy—a procedure in which providers take a small sample of tumor tissue. During a biopsy, a doctor uses a needle to remove a small piece of tissue from the tumor. This sample is then sent to a laboratory where a pathologist examines the cells under a microscope to determine what kind of tumor it is.[3]
In addition to examining the cells’ appearance, doctors also use molecular and genetic testing to confirm the diagnosis. These specialized tests look for the specific genetic changes that characterize myxoid liposarcoma, such as the FUS-DDIT3 or EWSR1-DDIT3 fusion genes. Finding these genetic markers helps confirm that the tumor is indeed myxoid liposarcoma and not another type of tumor that might look similar under the microscope.[1]
Once myxoid liposarcoma is diagnosed, doctors also check whether the cancer has spread to other parts of the body. This typically involves additional imaging tests, such as chest X-rays or CT scans of the chest, to look for signs that the tumor has spread to the lungs or other organs.[3]
How Changes Occur in the Body
Understanding what happens inside the body when myxoid liposarcoma develops can help patients better grasp the nature of their condition. At its core, myxoid liposarcoma begins when normal fat cells undergo genetic changes that cause them to behave abnormally. Instead of growing and dividing in a controlled manner, these cells multiply uncontrollably and form a mass or tumor.[1]
The tumor cells in myxoid liposarcoma have a distinctive appearance under the microscope. They produce a gel-like, mucus-like substance called myxoid material that fills most of the tumor. This substance gives the tumor its characteristic appearance and is where the “myxoid” part of the name comes from. The presence of this material makes the tumor feel soft when examined.[6]
As the tumor grows, it occupies more space within the tissue where it develops, most commonly deep within the muscles of the thigh or other limbs. Because these tumors often develop in the intermuscular fascial planes—the layers of tissue that separate different muscle groups—or in other deep-seated areas, they may not be visible or noticeable until they reach a substantial size.[8]
When the tumor grows large enough, it can begin to press on surrounding structures. If it presses against nerves, it can cause pain, numbness, or weakness in the affected limb. If it affects muscles, it can limit movement or cause discomfort during physical activity. In cases where the cancer spreads, tumor cells can travel through the bloodstream or lymphatic system to other parts of the body, where they establish new tumors in soft tissues, bones, or organs.[1]
The genetic fusion between the FUS and CHOP genes appears to play a central role in causing cells to become cancerous. Laboratory studies suggest this fusion gene disrupts normal cellular processes and allows cells to grow without the usual controls. Researchers believe the fusion gene may interfere with important regulatory proteins that normally prevent excessive cell growth, though the exact mechanisms are still being studied.[3]
Treatment Approaches
Treatment for myxoid liposarcoma typically involves one or more approaches, depending on the tumor’s size, location, whether it contains round cells, and whether it has spread to other parts of the body. The primary treatment for most cases is surgery, though radiation therapy and chemotherapy may also play important roles.[1]
Surgery is the main treatment for myxoid liposarcoma. A surgeon removes the tumor along with surrounding healthy tissue, including any microscopic tumor cells that might not be visible to the naked eye. Taking out this margin of normal tissue around the tumor helps reduce the risk of the cancer coming back, a situation called recurrence. The goal of surgery is to remove the entire tumor while preserving as much normal function of the affected limb or area as possible. In rare cases, if the tumor is very large or affects critical structures, surgical amputation may be necessary, though this is uncommon.[4]
Radiation therapy uses high-energy radiation to kill cancer cells. Providers often use radiation therapy in combination with surgery. Radiation may be given before surgery to shrink the tumor, making it easier to remove completely. It can also be given after surgery to kill any remaining cancer cells and reduce the risk of the cancer returning. Myxoid liposarcoma is known to respond well to radiation therapy, making it an important part of treatment for many patients.[1][4]
Chemotherapy involves using drugs to kill cancer cells throughout the body. Healthcare providers may use chemotherapy to treat tumors that cannot be removed by surgery, when the cancer has spread to other parts of the body, or in cases that are difficult to manage with surgery and radiation alone. Myxoid liposarcoma, particularly the pure myxoid form without round cells, tends to be relatively sensitive to chemotherapy compared to some other types of soft tissue sarcomas. However, the decision to use chemotherapy depends on many factors specific to each patient’s situation.[1][14]
Treatment decisions are highly individualized. Factors that influence the treatment plan include the size and exact location of the tumor, whether it contains round cells and what percentage, whether the cancer has spread, the patient’s overall health, and the patient’s personal preferences. Because myxoid liposarcoma is rare, patients are encouraged to seek care from specialists who have experience treating this specific type of cancer.[3]
What to Expect After Treatment
After completing initial treatment for myxoid liposarcoma, patients enter a phase of ongoing monitoring called follow-up care. Regular follow-up appointments are essential because myxoid liposarcoma can come back in the same area or spread to other parts of the body, even after successful treatment.[4]
Follow-up care typically includes regular appointments with the healthcare team for several years after treatment. During these visits, doctors discuss any new symptoms, perform physical examinations to check for signs of the cancer returning, and may order imaging tests such as MRI or ultrasound if the examination raises concerns. Chest X-rays are commonly performed to check for any spread of cancer to the lungs, which is one of the more common sites where myxoid liposarcoma can spread.[4]
If myxoid liposarcoma does recur in the same area where it was originally treated—called a local recurrence—it is important to begin treatment again as quickly as possible. Treatment for recurrence may involve another surgery, additional radiation therapy, chemotherapy, or a combination of approaches.[4]
The long-term outlook for patients with myxoid liposarcoma varies depending on several factors. The location of the tumor in the body, whether the cancer has spread to other parts of the body, and how much of the tumor could be removed during surgery all affect prognosis. The presence and percentage of round cells in the tumor is also an important factor, with higher round cell content associated with poorer outcomes. 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]
Prevention Strategies
Because the exact causes of myxoid liposarcoma are not fully understood, there are no proven strategies to prevent this disease from developing. Unlike some other cancers where lifestyle changes can reduce risk—such as not smoking to reduce lung cancer risk—myxoid liposarcoma appears to develop primarily due to random genetic changes that cannot currently be prevented.[1]
However, being aware of risk factors can help some people take appropriate precautions. For individuals with genetic conditions such as Li-Fraumeni syndrome or neurofibromatosis that increase cancer risk, regular monitoring and screenings may be recommended by healthcare providers. These screenings cannot prevent cancer but may help detect it earlier when it is more treatable.[3]
For people who have had radiation therapy for another cancer, awareness of the increased risk of developing sarcomas later in life can be valuable. While this does not mean avoiding necessary radiation treatment when it is needed, it does underscore the importance of monitoring for new lumps or masses in the years following radiation exposure.[1]
The most important preventive measure available to everyone is vigilance about unusual lumps or masses. Any new lump that appears and persists, especially if it continues to grow, should be evaluated by a healthcare provider. While the vast majority of lumps are benign, prompt evaluation of any concerning lump is the best way to ensure early detection if cancer is present. Early detection generally leads to more treatment options and better outcomes.[5]
Maintaining overall good health through regular exercise, a balanced diet, and routine healthcare visits may support general well-being and help ensure that any health changes are noticed and addressed promptly, though these measures have not been specifically shown to prevent myxoid liposarcoma.[1]
