Sarcoma: Classifications

Bone Sarcomas

Three kinds of sarcoma occur within the bone, affecting the body’s skeletal structure.

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 percent 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.

Classic osteosarcomas show up in the ends of the bones and are considered aggressive tumors. Once surgically removed, they have little chance of recurring in the original site. However, they are more likely to spread to the lungs or leap to other bones.

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 actually 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 percent of these sarcomas begin in an arm or leg, 30 percent start in the trunk (torso) or abdomen, and 10 percent occur in the head or neck.

There are at least fifty different subtypes of soft-tissue sarcoma. 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) that 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)
  • Fibrosarcoma
  • Dermatofibrosarcoma
  • Low-grade fibromyxoid sarcoma

Nervous System

  • Malignant schwannoma
  • Malignant peripheral nerve sheath tumor
  • Blood vessels/vascular structures

Angiosarcoma

  • Hemangioendothelioma
  • 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

Fibrohistiocytic tumors

  • Malignant fibrous histiocytoma (MFH), also known as pleomorphic sarcoma
  • Myxoid fibrosarcoma