Sarcoma is a rare cancer that starts in connective tissues such as bone, cartilage, and muscle. It develops when the cells that make up these tissues (called mesenchymal cells) begin to grow out of control.
Some types of sarcoma are found in children, while others are more common in adults.
Most cancers are classified as carcinomas, which start in organs such as the lungs, breast, and colon and can be spread through the lymphatic system or blood to other areas of the body. Sarcomas are different, as they generally do not start in organs and rarely spread to the lymph glands. Rather they mostly travel through the blood stream and may eventually spread to the liver, lungs, and, rarely, the brain.
While sarcomas may arise anywhere in the body, they most often originate in the arms, legs, chest, or abdomen. Sarcomas are often not symptomatic until they are very large and may first be noticed as swelling or a painless lump. As they grow larger they can cause pain or soreness by pressing on surrounding nerves or muscles and eventually spreading to nearby organs. No one knows yet why some people develop these growths and others don’t.
Curing sarcoma usually depends upon discovering the tumor at an early stage. Because sarcomas represent less than 1% of all cancers and are rarely seen by most oncologists, finding the best care can be challenging. Proper management of sarcomas requires evaluation at a Comprehensive Cancer Center such as Columbia Cancer, because it is essential to start with an accurate diagnosis, which is mostly likely to come from a pathologist who frequently sees this rare disease.
Types of Sarcoma
Three kinds of sarcoma occur within the bone, with a diverse range of cellular and molecular features, making accurate diagnosis critical in finding the best treatment possible.
Osteosarcoma (“osteo” means bone) is a cancer of the developing bones and is most likely to be found during rapid growth in adolescence. Roughly 80% of these tumors originate in bones around the knee, though they can also be found in the thigh, upper arm, and shin bones. These sarcomas can often spread to the lungs and require both surgery to remove the original tumor and chemotherapy to treat any undetectable disease elsewhere in the body. With surgery and chemotherapy, this tumor is considered curable in the majority of cases.
The following subtypes of osteosarcoma grow at different rates and have different chances of spreading to other parts of the body:
- Parosteal sarcoma rarely penetrates the center of the bone or turns malignant. These tumors generally arise in the femur or behind the knee.
- Periosteal sarcoma is an aggressive tumor, affecting the tibia (the larger of the two bones between the knee and ankle). It is mostly made up of malignant cartilage.
- Osteosarcoma of the jaw and skull. Osteosarcoma of the facial bones is relatively rare and is generally found in patients between the ages of 20 and 40. Because these tumors are located in the head and neck, they tend to be diagnosed earlier and take longer to spread. Since they are difficult to remove surgically, local recurrence is more common.
- Telangiectatic osteosarcoma is a lesion affecting the long bones of the arms and legs. The prognosis (survival rates) for patients with these tumors has improved remarkably in the past few years.
Ewing’s sarcoma occurs primarily in children and young adults under 30. This condition affects large bones, such as the pelvis, shin, and thigh. It involves several types of sarcomas discovered by physician James Ewing in the 1920s and now called the Ewing Family of Tumors. These tumors are also treated with surgery and chemotherapy and the majority of patients with this sarcoma are cured of their disease. Radiation is also sometimes used on a case-by-case basis.
Primitive neuroectodermal tumors (PNET) have a similar molecular structure to Ewing’s sarcoma and are now considered to be the same disease. PNETs are very rare and often appear outside the bone.
Chondrosarcoma (“chondro” refers to cartilage) is a cancer of the flexible connective tissue in the larynx and respiratory tract, the outer ear, and on the surfaces of joints. These tumors are found in adults between the ages of 20 and 60. They usually start in the pelvis then move to other areas of the body. Chondrosarcoma accounts for roughly one third of all bone cancers. For these tumors, surgery is the primary treatment and they tend not to respond well to chemotherapy.
Soft-Tissue Sarcomas (STS)
Soft-tissue sarcomas affect both children and adults. About 60% of these sarcomas begin in an arm or leg, 30% start in the trunk (torso) or abdomen, and 10% occur in the head or neck.
There are at least fifty different subtypes of soft-tissue sarcoma (STS). The most common soft-tissue sarcomas are listed here, according to the body systems they affect. The two most common types of STS are liposarcomas, which start in fatty tissue, and gastrointestinal stromal sarcomas (GIST) which begin in the gastrointestinal tract. GIST tumors are unique in that, as cancer researchers have recently discovered, their growth is driven by a mutation in a gene called C-kit, which is not found in other sarcomas. This discovery led to the development of a drug called imatinib (or Gleevac), which blocks C-kit, causes significant tumor shrinkage, and reduces the risk of regrowth. The discovery of C-kit and the discovery of drugs that block it have revolutionized the treatment of this disease. Some of the other sarcoma types are listed below.
- Liposarcomas, including well-differentiated, dedifferentiated, myxoid, and pleomorphic
- Rhabdomysarcoma (RMS)
- Fibromatoses (desmoid tumors)
- Low-grade fibromyxoid sarcoma
- Malignant schwannoma
- Malignant peripheral nerve sheath tumor
- Blood vessels/vascular structures
- Hemangiopericytoma (Solitary Fibrous Tumor)
Sarcomas of Unknown Origin
- Alveolar soft part sarcoma (ASPS)
- Clear cell sarcoma (malignant melanoma of soft parts)
- Epithelioid sarcoma
- Synovial sarcoma
- Undifferentiated soft-tissue sarcoma
- Malignant fibrous histiocytoma (MFH), also known as pleomorphic sarcoma
- Myxoid fibrosarcoma
Sarcoma is a rare cancer. According to the American Cancer Society, only about 13,000 people will be diagnosed with soft-tissue sarcoma and only about 1,000 will be diagnosed with osteosarcoma.
Many people who are diagnosed with sarcoma have no identifiable risk factors, and no one knows exactly why these cancers develop. Some risk factors for sarcoma may include:
Radiation exposure (for the prior treatment of other cancers) may increase the likelihood of developing sarcoma. However, this accounts for fewer than 5% of all sarcomas. Recent advances in radiation therapy now allow physicians to target cancers much more precisely and to limit radiation doses, which may minimize these risks.
Some inherited conditions may increase an individual’s chance of developing sarcoma. These include:
- Gardner’s syndrome
- Li-Fraumeni syndrome
- Werner’s syndrome
- Gorlin syndrome
- Tuberous sclerosis
- Marfucci syndrome
- Oillier disease
Signs of Sarcoma
Sarcomas can grow without causing any symptoms. Pain or discomfort may occur only once these tumors grow large enough to press against the nerves or muscles.
A bone sarcoma may cause pain and/or swelling in an arm or leg, the trunk, the pelvis, or the back. This area may sometimes feel warm to the touch. Other symptoms include a limited range of motion in a joint, a fever for no known reason, or a bone that breaks from no apparent outward injury.
A soft-tissue sarcoma may cause pain or a feeling of fullness or difficulty breathing.
These symptoms are very general and may also be signs of other medical conditions.
Patients are naturally concerned when finding a lump in the arm, leg, or trunk of the body, yet it is important to remember that most lumps are not sarcomas. A lipoma, for example, is a very common benign growth—made of fat cells, not cancer cells. It is important to have any lump or swelling immediately evaluated by a physician.
Screening and Diagnosis
Symptoms of sarcoma aren’t always obvious, and there is no standard screening for sarcoma. Sarcomas can also develop gradually and be mistaken for other conditions. If you have any unusual lump or swelling, you should talk to your doctor. A sarcoma diagnosis can include the following:
Your doctor will take your medical history and ask about risk factors and family history. They’ll ask about any symptoms you may have had.
These noninvasive tests can show your care team things about a suspicious lump or help guide other diagnostic tests.
- X-ray of an area with a suspicious lump may be the first test your doctor orders. After diagnosis they may recommend a chest X-ray to see if the cancer has spread to the lungs.
- CT (computed tomography) scan takes data from several X-ray images of the body and converts them into pictures on a monitor. It can show tissues and blood vessels in addition to bones and is often done if your doctor thinks you may have a soft-tissue sarcoma in the chest or abdomen.
- MRI (magnetic resonance imaging) test uses powerful magnetic fields to create 3D pictures that can provide doctors with a detailed picture of the tumor and can sometimes even show the type of tissue it came from. These powerful images are often better than CT scans in looking at sarcomas in the arms or legs.
- Ultrasound uses soundwaves to show different parts of the body and can be used to see if a suspicious lump is a cyst (a noncancerous, fluid-filled sac), or if it may be a tumor.
- PET (positron emission tomography) scan uses a small amount of radioactive glucose injected into your vein to show where glucose is being used in your body. A scanner rotates around your body to create an overall picture. Cancer cells use more glucose than normal cells do.
If your doctor suspects sarcoma, they will order a biopsy to know for sure that it’s sarcoma. A biopsy takes a small tissue sample of the tumor to be looked at under a microscope, and sometimes other lab tests may be done on the sample as well. Biopsies are very important for sarcoma since there are so many different types. An accurate diagnosis is critical in finding the best treatment. Our pathologists at Columbia Cancer are highly trained in diagnosing sarcomas and have years of experience specializing in sarcoma specifically.
Biopsies, or a tissue sample of the suspected cancer, can be done in several different ways. Fine needle aspiration or core biopsy directly samples the suspicious lesion through your skin or guided by an endoscopic transesophageal ultrasound. If done through your skin with a local anesthetic, they’ll use a CT or ultrasound to guide the needle placement.
A biopsy can also help doctors visualize the cancer’s spread and determine if it can be removed, called staging.
When your doctor estimates your prognosis based on how much cancer is in your body and where it is, that’s called staging.
Grading the Tumor
Sarcomas are graded on a scale of 1–6. A low-grade tumor is generally easier to treat than a high-grade or more aggressive tumor. In order to determine the grade, physicians must perform a biopsy, which allows them to determine the type of tumor, its rate of growth, and how much of it is comprised of dead or dying tissue.
Sarcomas that have more normal cells and fewer dividing cells are called low-grade because they tend to be slow-growing and take longer to spread. Once the sarcoma has been graded, the grade is considered when determining its stage.
Staging the Tumor
The staging system for soft-tissue sarcoma is defined as follows:
- Stage IA: The tumor is smaller than 5 cm (2 inches) across and has not spread to lymph nodes or more distant sites. The cancer is grade 1 or the grade cannot be determined.
- Stage IB: The tumor is larger than 5 cm (2 inches) across and has not spread to lymph nodes or more distant sites. The cancer is grade 1 or the grade cannot be determined.
- Stage IIA: The tumor is smaller than 5 cm (2 inches) across. It has not spread to lymph nodes or more distant sites. The cancer is grade 2 or 3.
- Stage IIB: The tumor is larger than 5 cm (2 inches) across and has not spread to lymph nodes or more distant sites. The cancer is grade 2.
- Stage III: The tumor is larger than 5 cm (2 inches) across and has not spread to lymph nodes or more distant sites. The cancer is grade 3. OR: The tumor of any size and any grade has spread to nearby lymph nodes but not to distant sites.
- Stage IV: The cancer, of any size and any grade, has spread to lymph nodes near the tumor or to distant sites.