What is sarcoma?

A sarcoma is a type of cancer that starts in the body’s connective tissues. These tissues support and hold the body together and include bone, muscle, fat, blood vessels, nerves, and fibrous tissue (the tissue that gives structure and strength to organs). Because connective tissue is found throughout the body, sarcomas can begin almost anywhere. They most commonly occur in the arms, legs, and abdomen, but can also start in the chest, head and neck, or deep inside the body.

Sarcomas are malignant tumours, which means they can grow into nearby tissues and may spread (metastasize) to other parts of the body. This is different from benign tumours, which do not spread and usually grow more slowly. With early diagnosis and proper treatment, many sarcomas can be successfully managed.

What are the different types of sarcoma?

Sarcomas are grouped based on the type of tissue or cell where the cancer starts. There are two main groups — soft tissue sarcomas and bone sarcomas — and a smaller group called undifferentiated round cell tumours, which can affect either soft tissue or bone.

Soft tissue sarcomas

Soft tissue sarcomas start in the tissues that surround and support organs. There are many types, including:

• Adipocytic (fat) tumours: Examples include well-differentiated and pleomorphic liposarcoma.

• Fibroblastic tumours: Such as myxofibrosarcoma and dermatofibrosarcoma protuberans, which arise from fibrous connective tissue.

• Vascular tumours: Such as angiosarcoma, which begins in cells that line blood vessels.

• Pericytic tumours: Including malignant glomus tumour, which arises from cells surrounding small blood vessels.

• Muscle tumours: Such as leiomyosarcoma (smooth muscle) and rhabdomyosarcoma (skeletal muscle).

• Gastrointestinal stromal tumours (GIST): A type of sarcoma that starts in specialized cells in the wall of the digestive tract.

• Peripheral nerve sheath tumours, such as malignant peripheral nerve sheath tumour (MPNST), develop from the cells that cover nerves.

• Tumours of uncertain origin: Including synovial sarcoma, epithelioid sarcoma, and alveolar soft part sarcoma, which have distinctive genetic features.

Bone sarcomas

Bone sarcomas arise in bone-forming or cartilage-forming tissues. Common types include:

• Osteosarcoma: A cancer that produces new bone.

• Chondrosarcoma: A cancer that forms cartilage.

• Angiosarcoma of bone: A rare cancer of blood vessel–forming cells within bone.

• Other rare types: Such as chordoma and undifferentiated pleomorphic sarcoma of bone.

Undifferentiated round cell tumours

These rare cancers can affect children and adults and may begin in bone or soft tissue. They include tumours with specific genetic changes, such as Ewing sarcoma.

What causes a sarcoma?

In most people, the cause of sarcoma is unknown. However, several factors may increase the risk, including:

• Inherited genetic conditions: Such as Li-Fraumeni syndrome, neurofibromatosis type 1 (NF1), or familial retinoblastoma.

• Radiation exposure: Sarcomas sometimes develop years after radiation therapy for another cancer.

• Certain chemicals: Long-term exposure to some herbicides or industrial chemicals can increase risk.

• Chronic inflammation or injury: Long-standing inflammation in soft tissues or bone may slightly increase the chance of developing a sarcoma.

Even when risk factors are present, most people who develop sarcoma do not have an identifiable cause.

How is sarcoma diagnosed?

Diagnosis usually involves a combination of imaging tests and a biopsy, which is the most important step.

Imaging

Tests such as X-rays, CT scans, MRI scans, or PET scans help doctors see the tumour’s size, location, and whether it involves nearby structures.

Biopsy

A biopsy involves removing a small sample of tissue so a pathologist can examine it under a microscope. The biopsy confirms whether the tumour is a sarcoma and helps determine the specific type.

Genetic and molecular testing

Some sarcomas have unique genetic changes, such as gene fusions or mutations, that help confirm the diagnosis. These tests may also identify treatments that target specific genetic alterations.

Doctors may also order tests to check whether the tumour has spread to other parts of the body, such as the lungs or lymph nodes.

What information is included in the pathology report?

After examining tissue under a microscope, the pathologist prepares a report. For sarcoma, the report may include:

• Sarcoma type: The specific kind of sarcoma identified.

• Grade: How abnormal the tumour cells look and how quickly they are dividing. High-grade sarcomas tend to grow faster.

• Mitotic rate: A measure of how many cells are dividing.

• Necrosis: Whether there are areas of dead tumour tissue, which can indicate aggressive behaviour.

• Margins (if a tumour has been removed): Whether cancer cells are present at the edge of the removed tissue.

• Lymphovascular invasion: Whether tumour cells have entered blood vessels or lymphatic vessels.

• Genetic or molecular findings: Results from tests that help confirm the diagnosis.

This information helps guide treatment and provides important details about prognosis.

How are sarcomas treated?

Treatment depends on the type of sarcoma, its location, grade, and whether it has spread. Common treatments include:

• Surgery: The primary treatment for many sarcomas, aiming to remove the tumour completely.

• Radiation therapy: Often used before or after surgery to reduce the risk of recurrence.

• Chemotherapy: Used for some sarcoma types, especially those that tend to spread through the bloodstream.

• Targeted therapy: Treatments that block specific genetic changes found in certain sarcomas, such as GIST.

• Immunotherapy: Used for selected sarcoma types depending on their molecular features.

Your healthcare team will create a treatment plan based on the details in your pathology report and other clinical findings.

What is the prognosis for a person with sarcoma?

The prognosis depends on:

• The type of sarcoma.

• The size of the tumour.

• The grade (how aggressive it looks).

• The location of the tumour.

• Whether the sarcoma has spread to other parts of the body.

In general, sarcomas detected early and completely removed have a better prognosis. High-grade or advanced sarcomas may require more intensive treatment and have a higher risk of recurrence.

Your doctor will review your pathology report and imaging results to help you understand your specific situation.

Questions to ask your doctor

• What type of sarcoma do I have?

• Has my tumour spread or stayed in one area?

• What grade is the tumour, and what does that mean for my treatment?

• What treatments do you recommend, and why?

• Will I need surgery, radiation, chemotherapy, or targeted therapy?

• Are there genetic findings in my tumour that affect treatment options?

• What is the long-term outlook for this type of sarcoma?

• How often will I need follow-up appointments or imaging?