Myxofibrosarcoma is a rare type of cancer that grows in the connective tissue, most often appearing as a slow-growing lump under the skin of the arms or legs, primarily affecting older adults.
Understanding Myxofibrosarcoma
Myxofibrosarcoma is a form of cancer that begins in the body’s connective tissue, which is the framework that connects, supports, and surrounds other structures in the body, including bones, muscles, and organs. This cancer typically develops just beneath the skin, though it can sometimes grow in deeper tissues surrounding muscles. What makes this cancer particularly challenging is that it often grows in a way that spreads into nearby healthy tissue, making it harder to see where the cancer ends and healthy tissue begins.[1][2]
This type of cancer belongs to a larger family of cancers called soft tissue sarcomas, which are cancers that develop in the soft tissues of the body rather than in bones or organs. Among soft tissue sarcomas, myxofibrosarcoma is relatively common, particularly in older individuals. The cancer usually appears as a small lump that grows slowly over time, and many people don’t experience pain when it first develops. Because it can look harmless on the surface, people sometimes delay seeking medical attention until the lump has grown larger.[3]
Who Gets Myxofibrosarcoma: Epidemiology and Demographics
Myxofibrosarcoma is not a common cancer overall, but it represents one of the most frequent types of soft tissue sarcoma in older adults. The estimated incidence is less than 0.1 cases per 100,000 people each year, making it a relatively rare condition in the general population. In England, there are approximately 178 new cases diagnosed annually, which accounts for about 4.5% of all soft tissue sarcomas diagnosed in that country.[3][6]
This cancer shows a strong preference for older age groups. Most people diagnosed with myxofibrosarcoma are between 60 and 80 years old, with the average age at diagnosis falling somewhere between 50 and 70 years. It is quite rare for someone under the age of 30 to develop this type of cancer. This age pattern is important because it helps doctors consider myxofibrosarcoma when they see a suspicious lump in an older patient.[2][4][18]
There is also a slight difference in how often men and women develop this cancer. Men are somewhat more likely to be diagnosed with myxofibrosarcoma than women, though the difference is not dramatic. This gender pattern has been observed across multiple studies, though researchers don’t yet fully understand why this difference exists.[2][6]
The cancer most commonly affects the arms and legs, with the leg being the most frequent location. About 73.6% of cases occur in the lower limbs. Unlike some other types of sarcomas that tend to grow in the abdomen or trunk, myxofibrosarcoma rarely starts in these areas. This pattern of location is so consistent that when doctors see a soft tissue mass in an elderly patient’s leg, myxofibrosarcoma is often considered as a possible diagnosis.[1][3]
What Causes Myxofibrosarcoma
The exact cause of myxofibrosarcoma remains largely unknown, which is true for many types of cancer. Researchers are still working to understand what triggers the initial changes that lead to this disease. What scientists do know is that myxofibrosarcoma develops when cells in the connective tissue undergo changes in their DNA, which is the genetic material that contains instructions for how cells should behave.[1][2]
In healthy cells, DNA provides careful instructions about when to grow, when to divide into new cells, and when to die. These instructions ensure that the body maintains the right balance of cells. In cancer cells, however, DNA changes, also called mutations, give different instructions. These altered instructions tell cells to grow and multiply much faster than they should. Cancer cells also continue living when healthy cells would normally die. This creates an accumulation of abnormal cells that eventually form a tumor that can invade surrounding healthy tissue.[1][2]
High-grade myxofibrosarcoma, which is the more aggressive form of this cancer, displays highly complex genetic abnormalities. These tumors have multiple copy number alterations, meaning that certain sections of DNA are either duplicated too many times or deleted. However, despite this knowledge, the fundamental question of what causes these DNA changes in the first place remains poorly understood. More research is needed to identify the specific triggers that set this process in motion.[3]
Risk Factors for Developing Myxofibrosarcoma
Unlike some cancers where risk factors are well established, doctors have not identified specific risk factors unique to myxofibrosarcoma. This makes it difficult to predict who will develop this cancer or to take specific preventive measures. Age is the most consistent factor, with the risk being significantly higher in adults over 50, particularly those in their 60s to 80s. Being male also slightly increases the likelihood of diagnosis, though this is a modest risk factor.[2][4]
Some general risk factors that increase the chance of developing any type of sarcoma may also apply to myxofibrosarcoma, though this connection isn’t definitively proven. These broader risk factors include certain genetic conditions that make people more prone to developing sarcomas in general. Examples include Li-Fraumeni syndrome and neurofibromatosis Type 1, both of which are inherited conditions that increase cancer risk.[2]
Exposure to certain chemicals has also been linked to increased sarcoma risk. Substances such as arsenic and certain herbicides have been identified as potential risk factors. People who work with or are exposed to these chemicals over long periods may have a higher risk, though the specific connection to myxofibrosarcoma needs more study.[2]
Previous radiation therapy is another factor that can increase sarcoma risk. People who have received radiation treatment for another cancer may develop a sarcoma in the area that was irradiated, sometimes many years after the initial treatment. This is an important consideration for cancer survivors who notice new lumps or masses developing in previously treated areas.[2]
Recognizing the Symptoms of Myxofibrosarcoma
The symptoms of myxofibrosarcoma can vary depending on where the tumor is located and how large it has grown. Many people with this cancer don’t have any symptoms at all in the early stages. The tumor can grow silently for some time before it becomes noticeable. This delay in symptom development is one reason why some cases are diagnosed only after the cancer has grown to a significant size.[2]
The most common symptom is a lump or swelling that appears under the skin, usually on an arm or leg. This lump typically grows slowly over weeks or months. One of the confusing aspects of myxofibrosarcoma is that it often doesn’t cause pain, especially in the early stages. A painless lump might not seem worrying to many people, which can lead to delays in seeking medical care. However, as the tumor grows larger, some people may begin to experience pain or discomfort in the affected area.[1][2][6]
In addition to the lump itself, swelling in the surrounding area can occur. This happens because the tumor can affect nearby tissues and may cause inflammation or fluid buildup. The size of the lump can vary considerably from person to person. Some tumors remain relatively small, while others can grow to the size of a golf ball or even larger before they are detected.[2][15]
The location of the tumor can influence what symptoms develop. A tumor near a joint might cause stiffness or limit movement. A tumor pressing on nerves might cause tingling, numbness, or weakness in the affected limb. A tumor located near the surface of the skin might be more easily noticed than one growing deeper in the tissue around muscles. Because myxofibrosarcoma most commonly occurs in the legs, symptoms related to walking or leg function may be the first signs that bring someone to medical attention.[1][12]
Prevention: What Can Be Done
Unfortunately, because the causes of myxofibrosarcoma are not well understood, there are no specific prevention strategies that can guarantee protection against this cancer. Unlike some cancers where lifestyle changes, vaccines, or screening programs can reduce risk, myxofibrosarcoma doesn’t have such clear preventive measures. This can be frustrating for people who want to take proactive steps to protect their health.[4]
However, there are some general health principles that may contribute to overall cancer prevention, even if they haven’t been specifically proven to prevent myxofibrosarcoma. Avoiding exposure to known carcinogenic chemicals, such as arsenic and certain herbicides, when possible is a sensible precaution. For people who work in industries where exposure to such substances is common, following proper safety protocols and using protective equipment is important.[2]
For people who have received radiation therapy in the past, being vigilant about any new lumps or changes in the treated area is wise. While this doesn’t prevent myxofibrosarcoma, early detection can lead to earlier treatment, which often results in better outcomes. Regular self-examination of the skin and underlying tissues, particularly in areas that have received radiation, can help identify problems early.[2]
The most important preventive action anyone can take is to seek medical attention promptly if they notice a lump or swelling that grows over time. While most lumps are not cancer, any persistent or growing mass deserves medical evaluation. Early diagnosis of myxofibrosarcoma can make treatment more effective and may reduce the risk of the cancer spreading or coming back after treatment.[1]
How Myxofibrosarcoma Changes the Body: Pathophysiology
Understanding how myxofibrosarcoma affects the body requires looking at what happens at the cellular and tissue level. This cancer begins in the connective tissue, which is made up of specialized cells and fibers that provide structure and support throughout the body. When myxofibrosarcoma develops, normal connective tissue cells transform into cancer cells that behave very differently from their healthy counterparts.[1][2]
One of the defining characteristics of myxofibrosarcoma is the type of tissue it produces. The cancer cells create an abnormal myxoid stroma, which is a jelly-like substance that fills the spaces between cells. This myxoid material is rich in mucopolysaccharides, which are complex sugars that make the tissue appear gelatinous. This distinctive feature is one reason the cancer has “myxo” (meaning mucus-like or slimy) in its name.[3]
Myxofibrosarcoma is graded into three categories based on how abnormal the cells look and how fast they are growing. Low-grade tumors have cells that look more similar to normal cells and grow more slowly. Intermediate-grade tumors fall somewhere in between. High-grade tumors have cells that look very abnormal and divide rapidly. The grade of the tumor correlates with how aggressive it is and how likely it is to spread to other parts of the body. High-grade myxofibrosarcoma has a worse prognosis because it can spread to distant sites, particularly the lungs, which is where this cancer most commonly metastasizes.[2][3]
One of the most problematic features of myxofibrosarcoma is its growth pattern. Unlike some tumors that form a distinct, well-defined mass, myxofibrosarcoma tends to have an infiltrative growth pattern. This means the cancer cells spread out like fingers into the surrounding healthy tissue, making it difficult to determine exactly where the tumor ends. This growth pattern is a major reason why myxofibrosarcoma has a high risk of coming back after surgery. Even when a surgeon removes what appears to be all of the visible tumor, microscopic cancer cells may have extended into nearby tissue that looked normal.[2][3]
When myxofibrosarcoma spreads to other parts of the body, a process called metastasis, it most commonly travels to the lungs. Cancer cells can break away from the main tumor and enter the bloodstream, eventually settling in the lungs where they can form new tumors. The likelihood of metastasis is closely related to the tumor grade, with high-grade tumors being much more likely to spread than low-grade ones.[2]
At the genetic level, myxofibrosarcoma cells show complex chromosomal abnormalities. High-grade tumors in particular display highly complex karyotypes (the full set of chromosomes) with multiple areas where genetic material has been gained or lost. These genetic changes contribute to the aggressive behavior of the cancer, though scientists are still working to understand exactly how these changes drive tumor growth and spread.[3]
