Metastatic sarcoma represents an advanced stage of a rare cancer that originates in bones and connective tissues, where the disease has spread beyond its original location to distant parts of the body, most commonly the lungs.

Understanding Metastatic Sarcoma

When we talk about metastatic sarcoma, we’re referring to a situation where sarcoma cancer cells have traveled from the place where they first appeared to other areas of the body. This happens when cancer cells break away from the original tumor and move through the bloodstream or through a network of vessels called the lymphatic system, which is part of the body’s immune defense. Even when sarcoma spreads to the lungs or bones, doctors still call it sarcoma rather than lung or bone cancer, because the cells remain sarcoma cells in nature.^[2]

According to medical research, around 83% of cases where soft tissue sarcoma spreads occur in the lungs. This makes the lungs the most common destination for metastatic sarcoma. Approximately one in four people with metastatic soft tissue sarcoma may develop this spread after they have already received initial treatment for their primary tumor.^[2]

Doctors may refer to metastatic sarcoma as stage 4 sarcoma. While most patients are diagnosed with localized disease, about 10% of people present with synchronous metastatic disease, meaning the cancer has already spread at the time of their first diagnosis.^[10]

Epidemiology

Sarcomas are rare cancers that make up only a small fraction of all cancer diagnoses. In adults, sarcomas account for just 1% of all cancers, though they represent a more significant proportion in younger populations, making up about 10% of cancers in children and 8% in adolescents and young adults.^[4]

In the United States, approximately 17,000 people receive a sarcoma diagnosis each year. This includes roughly 4,000 cases of bone sarcoma and about 13,000 cases of soft tissue sarcoma. At any given time, more than 50,000 patients and their families are dealing with sarcoma.^[5]

Despite being rare, sarcomas contribute substantially to lost years of life compared to many other cancers. This happens because sarcomas affect many children, adolescents, and young adults who would otherwise have many years ahead of them. In 2012, there were an estimated 1,410 deaths from bone cancers and 3,900 deaths from soft tissue cancers in the United States.^[4]

The distribution of sarcomas varies by age group. Soft tissue sarcomas occur more frequently in adults, while bone sarcomas are diagnosed more often in children, teenagers, and people older than 65 years. Bone sarcoma also occurs more frequently in males and in people who are Black or Hispanic.^[3]

Worldwide, the most common form of sarcoma is Kaposi’s sarcoma, which affected an estimated 42,000 people and caused about 20,000 deaths in 2018. Another common type, called gastrointestinal stromal tumor (GIST), affects between 4,000 and 6,000 people in the United States each year.^[14]

Causes

Sarcomas develop when immature bone or soft tissue cells undergo changes to their DNA. These changes cause the cells to develop into cancer cells that grow in an uncontrolled way. Over time, they may form a mass or tumor that can invade nearby healthy tissues. When left untreated, the cancer can travel through the bloodstream or lymphatic system from its original location to other organs, a process called metastasis. Once cancer has metastasized, it becomes much more challenging to treat.^[3]

Scientists don’t fully understand why some people develop sarcomas while the vast majority do not. The causes of sarcoma can vary depending on the specific subtype, and there are more than 100 distinct subtypes identified by the World Health Organization. Sarcomas can arise anywhere in the body and from various tissue structures including nerves, muscles, joints, bones, fat, and blood vessels, collectively referred to as the body’s connective tissues.^[5]

In healthy cells, DNA provides instructions that tell cells when to grow, multiply, and die. In cancer cells, the DNA changes tell cells to grow and multiply at uncontrolled rates and to continue living when they should die. This allows cancer cells to accumulate and form tumors.^[1]

Risk Factors

Several factors may increase a person’s risk of developing sarcoma. Understanding these risk factors doesn’t mean that someone will definitely develop the disease, but it helps identify people who may benefit from closer monitoring or preventive measures.

Exposure to certain chemicals represents one known risk factor. People who have been exposed to arsenic, certain chemicals used to make plastics like vinyl chloride monomer, herbicides containing phenoxyacetic acid, or wood preservatives containing chlorophenols may face increased risk.^[3]

Previous exposure to high doses of radiation, particularly from cancer treatment, can increase sarcoma risk. This means that people who have already been treated for one cancer with radiation therapy may face a higher chance of developing sarcoma later in life. Long-term swelling called lymphedema can also increase risk.^[3]

Some people inherit genetic conditions that increase their sarcoma risk. A small number of families have been identified in which more than one member in the same generation has developed sarcoma. There have also been reports of families where relatives of children with sarcoma develop other forms of cancer at unusually high rates. These family clusters represent a very small fraction of all cases and may be related to rare inherited genetic changes.^[5]

Certain inherited diseases are associated with increased risk of developing soft tissue sarcomas. These include Li-Fraumeni syndrome, which is associated with alterations in specific genes that normally help prevent cancer development.^[5]

Symptoms

The symptoms of metastatic sarcoma depend largely on where the cancer has spread and how large the tumors have grown. Because sarcomas can develop almost anywhere in the body, the symptoms can vary considerably from one person to another.

The most common sign of sarcoma is a lump that can be felt through the skin. This lump may or may not be painful. Because sarcomas are commonly hidden deep in the body, they are often diagnosed when they have already become quite large. Many lumps and bumps people develop are not cancerous, but it’s important to have them checked by a doctor at an early stage in case they are sarcoma.^[5]

For bone sarcomas, bone pain is a frequent symptom. Sometimes a bone may break with no clear cause, such as with only a minor injury or even no injury at all. This happens because the cancer has weakened the bone structure.^[1]

When sarcoma has spread to other parts of the body, symptoms may relate to the organs affected. Since the lungs are the most common site of metastasis, people may experience breathing difficulties, persistent cough, or chest pain. Some people with advanced sarcoma experience belly pain or unexplained weight loss.^[1]

The growth of a sarcoma causes pressure on nearby body tissues or organs. This pressure can lead to various symptoms depending on the location. For example, a tumor growing near nerves might cause numbness, tingling, or pain along the path of that nerve.^[9]

Prevention

Unfortunately, there are no specific screening tests or prevention strategies that can guarantee someone won’t develop sarcoma. However, understanding risk factors can help people make informed decisions about their health and safety.

People who work with or around hazardous chemicals should follow proper safety protocols to minimize exposure. This includes using protective equipment when handling chemicals known to increase sarcoma risk, such as vinyl chloride, certain herbicides, and wood preservatives.^[3]

For people receiving radiation therapy as treatment for another cancer, doctors carefully plan treatment to minimize radiation exposure to healthy tissues. The benefits of radiation therapy in treating the primary cancer typically outweigh the small risk of developing a secondary cancer like sarcoma years later.

Individuals with known genetic syndromes that increase sarcoma risk may benefit from genetic counseling and regular monitoring. This allows for earlier detection if cancer does develop, which may improve treatment outcomes.

Being aware of changes in your body is important. People should pay attention to any new lumps or bumps, especially those that are growing, and have them evaluated by a healthcare provider. While most lumps are harmless, early detection of sarcoma when it’s still localized offers the best chance for successful treatment.^[5]

Pathophysiology

The pathophysiology of metastatic sarcoma involves understanding how cancer cells change normal body functions as they grow, spread, and invade different tissues. This process happens at the cellular, tissue, and organ levels.

When sarcoma cells develop, they lose the normal controls that regulate cell growth and division. Normal cells have built-in mechanisms that tell them when to stop growing and when to die. Cancer cells bypass these controls, continuing to grow and divide without the usual limitations. This uncontrolled growth leads to the formation of a mass or tumor.^[3]

As the primary tumor grows, it can invade surrounding tissues. Sarcoma cells can grow into bone, nerves, and blood vessels. When cancer cells invade these structures, it usually indicates a poorer outlook for the patient. The invasion disrupts normal tissue function and can cause pain, loss of function, and other complications.^[18]

The process of metastasis begins when cancer cells break away from the primary tumor. These cells can enter the bloodstream or lymphatic system, which then carry them to distant parts of the body. The lungs are the most common destination because blood from most parts of the body passes through the lungs, creating many opportunities for circulating cancer cells to become trapped there.^[2]

Once cancer cells reach a distant site, they must be able to exit the blood vessels, survive in the new environment, and begin growing. This requires the cancer cells to have specific characteristics that allow them to adapt to different tissues. Not all cancer cells that enter the bloodstream successfully form metastases; many die before they can establish a new tumor.^[9]

Metastatic tumors can disrupt the function of the organs where they grow. For example, metastases in the lungs can interfere with breathing and oxygen exchange. Metastases in bones can weaken bone structure, leading to fractures. The presence of multiple metastatic tumors places additional stress on the body’s systems.^[3]

The grade of a sarcoma provides information about how quickly the cancer cells are growing and dividing, and how likely they are to spread. High-grade sarcomas have cells that look very different from normal cells and divide rapidly. These high-grade tumors are more likely to metastasize than low-grade sarcomas, which grow more slowly and whose cells look more like normal cells.^[8]