Cancer arises in cells that have undergone several genetic mutations that cause their growth to become abnormal.

In healthy cells, complex molecular mechanisms prevent cells from growing when they are not supposed to grow. It is thought that a series of genetic events occur wherein these molecular mechanisms are thrown off. The initial genetic event probably does not cause the cancer in its full-blown form, but rather throws the cell off-guard enough so that it will be certain to develop further genetic mutations and turn into a malignant tumor. The entire sequence of genetic changes in the cell are unknown for most cancers, including sarcomas.

For some tumors, translocations are important in the early development of the tumor. Translocations are events in which one piece of a chromosome breaks off and becomes stuck to another chromosome. This disrupts genes, turning off important "anti-growth" or tumor suppressor genes in some cases and turning on important "pro-growth" genes, also called oncogenes, in other cases.