Signs and symptoms of sarcoma include:

• A lump that can be felt through the skin that may or may not be painful
• Bone pain
• A broken bone that happens unexpectedly, such as with a minor injury or no injury at all
• Abdominal pain
• Weight loss

It's not clear what causes most sarcomas.

In general, cancer forms when changes (mutations) happen in the DNA within cells. The DNA inside a cell is packaged into a large number of individual genes, each of which contains a set of instructions telling the cell what functions to perform, as well as how to grow and divide.

Mutations might tell cells to grow and divide uncontrollably and to continue living when normal cells would die. If this happens, the accumulating abnormal cells can form a tumor. Cells can break away and spread (metastasize) to other parts of the body.

Factors that can increase the risk of sarcoma include:

• Inherited syndromes. Some syndromes that increase the risk of cancer can be passed from parents to children. Examples of syndromes that increase the risk of sarcoma include familial retinoblastoma and neurofibromatosis type 1.
• Radiation therapy for cancer. Radiation treatment for cancer increases the risk of developing a sarcoma later.
• Chronic swelling (lymphedema). Lymphedema is swelling caused by a backup of lymph fluid that occurs when the lymphatic system is blocked or damaged. It increases the risk of a type of sarcoma called angiosarcoma.
• Exposure to chemicals. Certain chemicals, such as some industrial chemicals and herbicides, can increase the risk of sarcoma that affects the liver.
• Exposure to viruses. The virus called human herpesvirus 8 can increase the risk of a type of sarcoma called Kaposi's sarcoma in people with weakened immune systems.