Germ Cell Tumors

Ovarian germ cell tumors develop from reproductive cells (germ cells) inside your ovaries. Ovaries are two small pelvic organs that play an important role in the female reproductive system. They produce eggs during your reproductive years. The germ cells inside your ovaries eventually mature (“germ”-inate) into eggs. With ovarian germ cell tumors, some of these cells clump together to form an abnormal mass instead.

Ovarian germ cell tumors usually form in just one ovary, but sometimes they appear in both.

Most ovarian germ cell tumors are benign (noncancerous). Rarely, they can be malignant (cancerous). These tumors can spread and damage healthy tissue. Malignant germ cell tumors are a rare form of ovarian cancer.

What are the types of ovarian germ cell tumors?

The most common types of ovarian germ cell tumors are:

• Mature teratoma (dermoid cyst): These benign tumors are the most common type of ovarian germ cell tumor. Most people diagnosed are in their teens, 20s or 30s.
• Dysgerminoma: This is the most common type of malignant ovarian germ cell tumor. But most of these tumors (70% of diagnoses) aren’t considered aggressive (fast-spreading) and respond well to treatment. Most people diagnosed are in their 20s or 30s.
• Immature teratoma: This is a fast-growing malignant tumor that can spread from your ovary to other parts of your body (metastasis). It’s most common in people 20 years old and younger.
• Yolk sac tumors (endodermal sinus tumors): These malignant tumors grow quickly and spread fast. They’re most common in people 20 years old and younger. Up to 40% of diagnoses involve children who are too young to have started their periods.
• Mixed germ cell tumors: These malignant tumors contain a mix of other tumor types, usually dysgerminoma and yolk sac tumors.

Rarer ovarian germ cell tumors include:

• Embryonal carcinoma.
• Choriocarcinoma.
• Polyembryoma.

How common are ovarian germ cell tumors?

Ovarian germ cell tumors are most common in people assigned female at birth (AFAB) in their reproductive years or younger. They account for up to 70% of ovarian growths in people between 10 to 30 years old. They’re less common in people over 40.

Approximately 95% of ovarian germ cell tumors are benign (mature teratomas). Only 2% to 3% of ovarian cancers are germ cell tumors.