Sarcoma

A sarcoma is a cancer that arises from transformed cells of mesenchymal (connective tissue) origin. Connective tissue is a broad term that includes bone, cartilage, fat, vascular, or hematopoietic tissues, and sarcomas can arise in any of these types of tissues. As a result, there are many subtypes of sarcoma, which are classified based on the specific tissue and type of cell from which the tumor originates. It is important to note that sarcomas are primary connective tissue tumors, meaning that they arise in connective tissues. This is in contrast to secondary (or 'metastatic') connective tissue tumors, which occur when a cancer from elsewhere in the body (such as the lungs, breast tissue or prostate) spreads to the connective tissue. The word sarcoma is derived from the Greek σάρξ sarx meaning 'flesh'. Sarcomas are typically divided into two major groups: bone sarcomas and soft tissue sarcomas, each of which has multiple subtypes. In the United States, the American Joint Committee on Cancer (AJCC) publishes guidelines that classify the subtypes of sarcoma. These subtypes are as follows: Subtypes of bone sarcoma: Subtypes of soft tissue sarcoma: Symptoms of bone sarcomas typically include bone pain, especially at night, and swelling around the site of the tumor. Symptoms of soft tissue sarcomas vary, but often present as firm, painless lumps or nodules. Gastrointestinal stromal tumors (a subtype of soft tissue sarcoma) often are asymptomatic, but can be associated with vague complaints of abdominal pain, a feeling of fullness, or other signs of intestinal obstruction. The cause of most bone sarcomas is not known, but several factors are associated with an increased risk of developing bone sarcoma. Previous exposure to ionizing radiation (such as prior radiation therapy) is one such risk factor. Exposure to alkylating agents, such as those found in certain cancer chemotherapeutic medicines, also increases the risk of bone sarcoma. Certain inherited genetic syndromes, including Li-Fraumeni syndrome, heritable RB1 gene mutations, and Paget's disease of bone, are associated with an increased risk of developing bone sarcomas. Most soft tissue sarcomas arise from what doctors call 'sporadic' (or random) genetic mutations within an affected person's cells. Nevertheless, there are certain risk factors associated with an increased risk of developing soft tissue sarcoma. Previous exposure to ionizing radiation is one such risk factor. Exposure to vinyl chloride (e.g., such as the fumes encountered in the production of polyethylene vinyl chloride (PVC)), arsenic and thorotrast all are associated with an increased risk of angiosarcoma. Lymphedema, such as that resulting from certain types of breast cancer treatment, also is a risk factor for development of angiosarcoma. As with bone sarcomas, certain inherited genetic syndromes also are associated with an increased risk of developing soft tissue sarcoma, including Li-Fraumeni syndrome, familial adenomatous polyposis, neurofibromatosis type 1, and heritable RB1 gene mutations. The mechanisms by which healthy cells transform into cancer cells are described in detail elsewhere (see Cancer main page; Carcinogenesis main page). The precise molecular changes that result in sarcoma are not always known, but certain types of sarcomas are associated with particular genetic mutations. Examples include: