Sarcomas of the Bone: The Basics

What is sarcoma?

Sarcoma is a cancer of the soft tissue (muscle, fat, nerve, or connective tissue) or bone. (This article will discuss sarcomas of the bone; soft tissue sarcomas will be discussed separately). Sarcomas encompass a group of over 40 different types of tumors. In general, sarcomas are considered quite rare, accounting for less than 1% of all adult cancer diagnoses, with approximately 10,000 new cases annually in the soft tissues and 2,400 new cases annually in the bone. Sarcomas are considered primary bone cancers (different from bone metastases from other cancers), and are named based on the site from which they arise. For example, chondrosarcomas arise from cartilage, osteosarcomas arise from bone, and fibrosarcomas arise from fibrogenic tissue.

Osteosarcoma is the most common type of bone sarcoma, accounting for approximately 35% of bone tumors. Chondrosarcoma is the second most common type in adults (accounting for 30% of bone sarcomas), and Ewing's sarcoma is the second most common type in children. All other types are extremely rare, each accounting for less than 1% of all bone sarcomas. (See list below for some types of sarcomas of the bone). Within these types, there are further subtypes -- for example, there are 11 different types of osteosarcomas.

Ewing’s sarcoma can occur in the bone or soft tissue (called extra-osseous), and this is important when treatment options are considered. The large majority of cases occur in the bones, and the diagnosis is most common in the teenage years. PNET (primitive neuroectodermal tumor) is a type of sarcoma closely related to Ewing’s. PNET can occur in the bone or the central nervous system. PNET of the bone is treated the same as Ewing’s sarcoma, but PNET in the brain or spinal cord is a genetically different tumor that is treated differently. Ewing’s, PNET, Askin’s tumors and neuroepithelioma all contain the same genetic abnormality, called an 11-22 chromosomal translocation (t11;22). Because of this similarity, these tumors are referred to as the Ewing’s sarcoma family of tumors and are treated similarly.

Am I at risk for sarcoma?

The cause of sarcoma of the bone (SB) is unknown in the large majority of cases. SB can develop from benign lesions in the bone or in areas that previously received radiation (these cases are rare and tend to occur many years after the radiation). In addition, a familial genetic syndrome called Li Fraumeni and a disease called Paget's are associated with sarcomas. For the most part, doctors do not know why SBs occur and therefore cannot determine who is at risk of developing the disease.

The rates of osteosarcoma and Ewing’s sarcoma are the same for boys and girls until 13 years of age, after which males are more commonly affected. Ewing’s is 10 times more common in Caucasians then in blacks (either American or African) or Asians.

What screening tests are available?

Unfortunately, there is no screening test for SB. Screening tests are developed for the early detection of common or very deadly diseases. Given how rare SBs are, they would be difficult to screen for in the general population. In addition, the number of different types of SB would make it very difficult to develop one single screening test that could detect all types.

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