Germ cell tumors are growths formed from reproductive cells. Tumors can be cancerous or non-cancerous. Most germ cell cancers are in the form of testicular cancer or ovarian cancer. Some germ cell tumors develop in other parts of the body, such as the abdomen, brain and rib cage, although it is not known. Germ cell tumors found elsewhere than in the testes and ovaries (extragonadal germ cell tumors) are very rare. Germ cell tumors usually respond to treatment and many can be cured, even if they are diagnosed late.