A sarcoma is a cancer that develops from particular tissues, such as muscle or bone. There are two types of sarcoma: osteosarcoma, which develops from bone, and soft tissue sarcoma. Soft tissue sarcoma can arise from muscle, fat, nerves, cartilage, or blood vessels. Cancerous tumors can develop when abnormal cells in these tissues multiply and grow out of control. Scientists do not yet fully understand why these cells become abnormal. However, most cancers are thought to develop due to genetic changes (mutations).
The tumor is named based on the type of tissue it resembles. For example, a soft tissue sarcoma that looks like fat is called a liposarcoma; a tumor that looks like fibrous tissue is called a fibrosarcoma. If a soft tissue sarcoma resembles more than one type of tissue, its name will reflect its complex appearance. For example, a neurofibrosarcoma develops in the fibrous tissue surrounding a nerve. A soft tissue sarcoma that doesn't look like any normal tissue is undifferentiated or unclassified.
More than half of soft tissue sarcomas develop in the arms and legs. About one-third develop in the trunk. Few develop in the head and neck. Most soft tissue sarcomas occur in adults over age 55. But about one-fifth of these tumors occur in children. In children, soft tissue sarcomas are twice as common in whites as in African Americans.
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