Germ cell tumors begin in the reproductive cells (egg or sperm) of the body. In women, this type begins in the cells that form eggs in the ovaries, known as germ cells.

Benign Germ Cell Tumors
Most germ cell tumors are benign (non-cancerous).  Mature teratomas are the most common type of benign germ cell tumor.  These tend to occur in women of reproductive age (teens through forties) and are often called a dermoid cyst.  Women with benign germ cell tumors such as mature teratomas are treated by removing the part of the ovary that has the tumor (ovarian cystectomy) or by removing the entire ovary.  There may be few symptoms.  Abdominal pain or constipation may occur, and when the tumor gets bigger, an abdominal mass may be evident.

Malignant Ovarian Germ Cell Tumors
Ovarian germ cell malignant tumors are uncommon and account for approximately 5 percent of ovarian cancer cases. They can occur in women of any age but are more often found in young women or adolescent girls. These tumors frequently affect only one ovary and are generally curable if found and treated early.

Immature Teratomas
Immature teratomas are a type of malignant ovarian germ cell tumors.  They typically occur in girls and young women under 18.  In cases where tumors have not spread beyond the ovary, they are treated by surgical removal of the ovary.  If they have spread beyond the ovary, chemotherapy is typically recommended in addition to surgery.

Dysgerminoma
While ovarian germ cell tumors are rare, this subtype, dysgerminoma, is the most common malignant form and typically affects women in their teens or twenties.  These types of tumors do not grow or spread quickly and are usually treatable.  If confined to the ovary, more than 75% of women are cured by the removal of the ovary, and if the cancer has spread, surgery along with radiation and/or chemotherapy can control and/or cure the disease in approximately 90% of patients.  New types of treatment are being tested through clinical trials, such as high-dose chemotherapy with bone marrow transplant.

Malignant germ cell tumors of the ovary follow the same staging system as epithelial cancers and primary peritoneal cancers.