Rhabdomyosarcoma is a rare type of cancer that starts in the soft tissues of the body, most commonly in skeletal muscle. Although it can develop anywhere, this aggressive disease most frequently affects children and teenagers, making it the most common soft tissue sarcoma in young people. Understanding this condition, its symptoms, and risk factors can help families recognize warning signs early and seek appropriate medical care.
Understanding Rhabdomyosarcoma: What Happens in the Body
Rhabdomyosarcoma develops when immature muscle cells fail to develop properly and instead become cancerous. These abnormal cells, called rhabdomyoblasts, multiply uncontrollably and form tumors. While the disease typically starts in skeletal muscle tissue—the muscles that help us move our arms, legs, and other body parts—it can actually begin in many different locations throughout the body.[1][2]
The body’s skeletal muscles are normally made up of cells that grow and develop in an organized way. In rhabdomyosarcoma, something goes wrong during this development process. The muscle cells that should mature into healthy tissue instead transform into cancer cells. These cancerous cells retain characteristics of very early, primitive muscle cells, similar to those found in developing embryos. This is why one type of the disease is called “embryonal” rhabdomyosarcoma—it resembles the muscle cells of a six to eight-week-old embryo.[5]
The disease is classified into several distinct types, each with different characteristics and behaviors. Embryonal rhabdomyosarcoma is the most common form, accounting for about 60 to 70 percent of childhood cases. It typically affects younger children, especially those under age six, and most often develops in the head and neck area or in the urinary and reproductive systems.[3][4]
Alveolar rhabdomyosarcoma tends to affect older children, teenagers, and young adults between ages 20 and 35. This type is considered more aggressive, meaning it grows quickly and spreads more readily to other parts of the body. Alveolar rhabdomyosarcoma most commonly develops in the arms, legs, or trunk of the body.[2][6]
Pleomorphic rhabdomyosarcoma is rare in children and instead typically affects adults age 50 and older. It can develop anywhere in the body but most often appears in the legs, arms, chest, abdomen, or areas of the head and neck.[2][4]
There is also a spindle cell/sclerosing type, which can occur at various ages. One subtype is more common in infants and affects the trunk area, while another can affect children, adolescents, and adults, often appearing in the head and neck region.[3][6]
How Common Is Rhabdomyosarcoma?
Rhabdomyosarcoma is considered a rare disease. In the United States, between 400 and 500 people receive a diagnosis each year. To put this in perspective, the incidence rate is approximately 4.71 cases per million children and adolescents under age 20.[2][26]
Despite being rare overall, rhabdomyosarcoma holds the unfortunate distinction of being the most common type of soft tissue sarcoma diagnosed in children. It accounts for about 40 percent of all soft tissue sarcomas in young people and roughly 3 percent of all childhood cancers combined.[4][5][26]
The disease shows distinct patterns based on age. More than half of all cases occur in children younger than 10 years old. There is a peak in incidence during early childhood, particularly in children under age four, when the rate reaches about 6.5 cases per million. A second, smaller peak occurs during adolescence, possibly related to the rapid growth that happens during puberty.[26]
Rhabdomyosarcoma affects boys slightly more often than girls, with a male-to-female ratio of about 1.37 to 1. This male predominance is particularly noticeable in the embryonal subtype, where the ratio increases to 1.51 males for every female diagnosed.[26]
The disease does not appear to favor any particular racial or ethnic group—it affects children of all backgrounds at similar rates. While only 1 to 2 percent of rhabdomyosarcoma cases occur in adults, when it does affect adults, it tends to be the pleomorphic type.[4][5]
What Causes Rhabdomyosarcoma?
Scientists do not yet fully understand what causes rhabdomyosarcoma. The disease develops when immature muscle cells undergo genetic mutations that transform them into cancer cells. These mutated cells then multiply rapidly and create tumors instead of developing into healthy muscle tissue.[2][17]
Research has identified certain genetic changes that may play a role in causing some forms of the disease. For example, a specific genetic mutation that creates what’s called the fusion gene PAX/FOX01 has been linked to alveolar rhabdomyosarcoma. This abnormal gene is created when pieces of two different genes join together incorrectly, resulting in cells that grow out of control.[2][17]
In most cases, rhabdomyosarcoma occurs sporadically, meaning it happens by chance without any clear cause or pattern. The genetic mutations that lead to the cancer are not inherited from parents but instead occur randomly during a child’s development. The vast majority of children who develop rhabdomyosarcoma have no family history of the disease and no known risk factors.[3][4]
Researchers continue to study what might trigger these genetic changes. Unlike many adult cancers, rhabdomyosarcoma in children is not linked to lifestyle factors such as smoking, diet, or sun exposure. The disease appears to develop from errors that occur during normal cell division and growth, though the exact mechanisms remain under investigation.[3][6]
Risk Factors for Rhabdomyosarcoma
While most children who develop rhabdomyosarcoma have no identifiable risk factors, certain rare inherited genetic conditions are known to increase the chances of developing the disease. It’s important to understand that even with these conditions, the actual risk of developing rhabdomyosarcoma remains relatively low.[3][6]
Li-Fraumeni syndrome is a rare genetic disorder that makes individuals more likely to develop various types of cancer at some point in their lives. People with this condition have an increased risk of rhabdomyosarcoma, along with several other cancers. The syndrome is caused by mutations in a gene called TP53, which normally helps prevent tumor formation.[2][3][7]
Beckwith-Wiedemann syndrome is a congenital disorder present from birth that can cause excessive growth in various parts of the body, including internal organs. Children with this condition may have an increased risk of developing several types of childhood tumors, including rhabdomyosarcoma.[2][3][7]
Neurofibromatosis type 1 is a genetic condition that causes tumors to grow on nerve tissue throughout the body. While most of these tumors are benign (not cancerous), individuals with neurofibromatosis type 1 have a slightly higher risk of developing various cancers, including rhabdomyosarcoma.[2][3][6]
Costello syndrome is a rare disorder that affects multiple organ systems and causes developmental delays, distinctive facial features, and other health problems. Children with Costello syndrome have an increased risk of developing certain tumors, including rhabdomyosarcoma.[2][3][7]
Noonan syndrome is a genetic disorder that can cause unusual facial characteristics, short stature, heart defects, and other physical problems. Individuals with this condition may have a slightly elevated risk of developing rhabdomyosarcoma.[3][6][7]
Additional rare syndromes associated with increased risk include DICER1 syndrome and cardiofaciocutaneous syndrome. DICER1 syndrome is a genetic condition that can lead to cancer developing in affected children, while cardiofaciocutaneous syndrome is another rare disorder affecting development.[2][3][7]
One non-genetic factor that has been identified is birth weight. Children who had a high birth weight or were larger than expected at birth may have a slightly increased risk of developing embryonal rhabdomyosarcoma, though the reasons for this association are not fully understood.[3][6][13]
Recognizing the Symptoms of Rhabdomyosarcoma
The symptoms of rhabdomyosarcoma vary widely depending on where in the body the tumor develops and how large it grows. Because the cancer can start in so many different locations, it can cause a diverse range of symptoms. Sometimes the first sign is simply a lump or swelling that keeps getting bigger or doesn’t go away.[1][3]
When rhabdomyosarcoma develops in the head and neck region, it may cause headaches, particularly if the tumor grows large enough to press on surrounding structures. A tumor near the eyes can cause the eye to bulge outward, swell, or tear excessively. In some cases, children may develop crossed eyes or vision problems. If the tumor forms in the nose, throat, or ears, it can cause bleeding from these areas, nosebleeds, or ear discharge.[1][2][7]
Rhabdomyosarcoma in the urinary or reproductive system often causes difficulties with normal bodily functions. Children may have trouble urinating or experience blood in their urine, a condition called hematuria. Bowel movements may become difficult, and there may be blood visible in the stool. In girls, a mass or lump may grow from the vagina. In boys, a fast-growing mass or lump may appear around the testicles.[1][2][3]
When the tumor develops in the arms or legs, the most common symptom is a lump or swelling in the affected limb. This may or may not be painful. The lump typically continues to grow larger over time. If the tumor presses on nearby nerves or other structures, it can cause discomfort in the surrounding area.[1][2][7]
Tumors that form deep within the abdomen or belly area may cause abdominal pain, vomiting, or constipation. These symptoms can be vague and easily mistaken for more common digestive problems, which sometimes delays diagnosis.[2][17]
As the disease progresses or if it spreads to other parts of the body, additional symptoms may develop. These can include persistent bone pain, constant coughing, general weakness, and unexplained weight loss. Some children may develop jaundice, a yellowing of the skin and eyes, if the tumor affects the bile ducts in the liver area.[24][26]
One challenging aspect of rhabdomyosarcoma is that its symptoms can resemble those of many less serious, more common childhood conditions. A lump might initially be dismissed as a bruise or minor injury. Nosebleeds, vomiting, and digestive issues can all have innocent explanations. However, symptoms that persist, don’t improve with time, or seem to be getting worse should always be evaluated by a healthcare provider.[2][17]
In some cases, particularly when tumors develop deep within the body, there may be few or no noticeable symptoms until the tumor grows quite large. This is why regular medical checkups are important and why any unusual changes in a child’s health should be taken seriously.[7][24]
Can Rhabdomyosarcoma Be Prevented?
Unfortunately, there are no known ways to prevent rhabdomyosarcoma. Because the disease typically occurs randomly and is not linked to lifestyle factors or environmental exposures in children, there are no specific prevention strategies that families can follow to reduce risk.[3][6]
Most children who develop rhabdomyosarcoma have no identifiable risk factors, and the genetic mutations that cause the disease appear to occur by chance during normal growth and development. Unlike many adult cancers, rhabdomyosarcoma is not associated with smoking, diet, physical activity, or other modifiable behaviors.[3][4]
For families with a history of the rare genetic syndromes associated with increased rhabdomyosarcoma risk, such as Li-Fraumeni syndrome or Beckwith-Wiedemann syndrome, genetic counseling and testing may be helpful. Healthcare providers can help these families understand their specific risks and discuss whether enhanced monitoring or screening might be appropriate, though it’s important to note that even in these cases, the overall risk of developing rhabdomyosarcoma remains relatively low.[2][3]
While prevention is not possible, early detection can make a significant difference in outcomes. Being aware of the symptoms and seeking prompt medical evaluation for any persistent or worsening symptoms is the most important step parents and caregivers can take. Regular pediatric checkups also provide opportunities for healthcare providers to identify any unusual findings that might warrant further investigation.[2][7]
For children who have been treated for rhabdomyosarcoma, long-term follow-up care is essential. While this doesn’t prevent the disease, it helps monitor for any recurrence and manages the long-term effects of treatment. Survivors of childhood cancer may face various health challenges later in life, and continued medical care helps address these issues as they arise.[19][22]
How Rhabdomyosarcoma Changes the Body
Understanding how rhabdomyosarcoma affects normal body functions requires looking at what happens when cells behave abnormally. In healthy development, primitive muscle cells follow a carefully controlled process of growth and specialization, eventually becoming mature skeletal muscle tissue that can contract and help the body move. In rhabdomyosarcoma, this normal development process goes awry.[4][5]
The cells that should develop into functional muscle tissue instead remain in an immature state and begin multiplying uncontrollably. These cancer cells retain characteristics of very early embryonic muscle cells but never complete their normal development. Instead of forming organized muscle tissue, they create masses of abnormal cells that form tumors.[4][5]
As the tumor grows, it takes up space and puts pressure on surrounding tissues and organs. This mechanical pressure is responsible for many of the symptoms people experience. For example, when a tumor develops behind the eye, it physically pushes the eyeball forward, causing it to bulge. When a tumor grows in the urinary tract, it can partially block the flow of urine, making urination difficult or painful.[1][2]
Rhabdomyosarcoma cells can invade nearby tissues, breaking through normal tissue boundaries and infiltrating surrounding structures. This invasive growth is one characteristic that distinguishes cancer from benign tumors. The cancer cells essentially ignore the normal signals that tell cells where they should and shouldn’t grow.[4][5]
One of the most concerning aspects of rhabdomyosarcoma is its ability to spread beyond the original tumor site. Cancer cells can break away from the primary tumor and travel through the bloodstream or lymphatic system—the network of vessels and organs that help the body fight infection. These traveling cancer cells can establish new tumors in distant parts of the body, a process called metastasis.[5][12]
Common sites where rhabdomyosarcoma spreads include the lungs, bone marrow, bones, and lymph nodes. When cancer cells reach the lungs, they can interfere with breathing and oxygen exchange. In the bone marrow, they can disrupt the normal production of blood cells, potentially causing fatigue, increased infections, or easy bruising and bleeding. Spread to the bones can cause pain and weaken the skeletal structure.[5][26]
The biochemical changes in rhabdomyosarcoma cells are complex. These cells have genetic mutations that cause them to produce abnormal proteins and ignore the normal cellular mechanisms that control growth and death. Healthy cells have built-in programs that cause them to die when they become damaged or old, but cancer cells evade these death signals and continue multiplying indefinitely.[4][5]
Rhabdomyosarcoma tumors also trigger the formation of new blood vessels, a process called angiogenesis. The tumor essentially hijacks the body’s normal blood vessel formation mechanisms to create its own blood supply. These new blood vessels deliver oxygen and nutrients that help the tumor grow, and they also provide pathways for cancer cells to enter the bloodstream and spread to other locations.[4][12]
The body’s immune system, which normally identifies and destroys abnormal cells, often fails to effectively combat rhabdomyosarcoma. Cancer cells can develop ways to hide from immune detection or actively suppress immune responses. This allows the tumor to continue growing even though the body has sophisticated defense mechanisms designed to prevent exactly this type of abnormal cell growth.[12]
As rhabdomyosarcoma progresses, it can cause systemic effects throughout the body. Children may experience fatigue, weight loss, and general feelings of unwellness. These symptoms occur partly because the tumor consumes resources that the body needs for normal functioning and partly because of the body’s inflammatory and immune responses to the cancer.[24][26]
