Causes

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.