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) and are called teratomas.  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. Benign germ cell tumors may grow rapidly and present with symptoms such as abdominal pain, fluid build up in the abdomen and ovarian torsion (which can cause significant pain). They may also cause an increase in a hormone known as bHCG.   Abdominal pain or constipation may occur, and when the tumor gets bigger, an abdominal mass may be evident.

Malignant Ovarian Germ Cell Tumors

Malignant Ovarian germ cell 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 with surgery and chemotherapy.

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. Malignant immature teratomas are 100 times less common than benign mature teratomas. 

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 with surgery, sometimes in combination with chemotherapy or possibly radiation in advanced stage cases.

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

Yolk Sac Tumors
Yolk sac tumors, also known as endodermal sinus tumors, account for about 15% of germ cell tumors. The median dian age at diagnosis is 18-19. About 40% of patients are diagnosed  prior to puberty. These cancers tend to grow rapidly and metastasize quickly, making treatment more challenging.