Test Your Knowledge

Many types of growths or tumors can form in the ovaries. Some are noncancerous (benign) and never spread outside of the ovary. For example, women who are still menstruating can develop benign cysts on their ovaries that can be felt during a pelvic examination or seen with use of imaging tests such as x-rays.

Women with noncancerous tumors can be successfully treated by removing one of their ovaries (unilateral oophorectomy) or the portion of the ovary that houses the tumor (partial oophorectomy). Other types of tumors that begin in the ovaries are cancerous (malignant) and can potentially invade other parts of the body.

Ovarian tumors are generally named according to the type of cells in which they originate and whether or not the tumor is cancerous. The three main types of ovarian tumors include germ cell tumors, stromal cell tumors and epithelial tumors.

Germ cell tumors originate in the cells that produce the eggs (ova). They account for about 5 percent of ovarian cancers, according to the American Cancer Society (ACS). There are numerous subtypes of these tumors, the majority noncancerous. However, some germ cell tumors are malignant and may be life-threatening. Types of germ cell ovarian tumors include:

• Teratoma. The benign form of this germ cell tumor is called mature teratoma, and it is the most common type of ovarian germ cell tumor. It typically affects women in their childbearing years. The malignant germ cell tumor is called immature teratoma. This type usually affects girls under age 18. These rare cancers resemble fetal or embryonic tissue, such as respiratory passages, connective tissue and the brain.
  
  
• Dysgerminoma. Although this cancer is rare, it is the most common ovarian cancer that arises in the germ cells. Dysgerminoma typically affects women in their teens and 20s. These tumors are considered malignant but they usually do not develop or spread quickly. Women with dysgerminoma usually have a good prognosis (predicted outlook or chance of survival), regardless of the stage of the cancer.
  
  
• Endodermal sinus tumor (or yolk sac tumor) and choriocarcinoma. These tumors are very rare and usually affect girls and young women. They tend to develop and spread quickly, but are often sensitive to treatment.
  
  Choriocarcinomas typically begin during pregnancy in the placenta instead of the ovary, and these tumors are normally more responsive to treatment than ovarian choriocarcinomas.
  
  

  

Stromal cell tumors begin in the cells of connective tissue that keep the ovary intact and produce estrogen and progesterone, the female hormones. More than half of stromal tumors are found in patients older than 50 years of age, according to the ACS. However, some of these tumors affect young girls. Some stromal tumors produce female hormones, and occasionally some may produce male hormones. Granulosa cell tumors are a cancerous type of stromal tumor. Other malignant stromal tumors include granulosa-theca tumors and Sertoli-Leydig cell tumors, which are generally considered low-grade cancers. Benign stromal tumors include thecomas and fibromas.

Epithelial tumors begin in the cells that cover the ovary’s outer surface. Types of epithelial tumors include:

• Benign epithelial ovarian tumors. The majority of epithelial ovarian tumors are noncancerous, do not spread to other parts of the body and typically do not cause serious illness. There are a variety of these tumors, including mucinous adenomas, serous adenomas and Brenner tumors.
  
  
• Malignant epithelial ovarian cancers. These carcinomas account for about 85 to 90 percent of ovarian cancers, according to the ACS. Several features of epithelial ovarian carcinoma cells can be viewed under a microscope. These features are used to categorize malignant epithelial ovarian carcinomas into four differentiated subtypes: mucinous, serous, endometrioid and clear cell. Undifferentiated epithelial ovarian carcinomas do not resemble any of these four subtypes, and tend to develop and spread more quickly.
  
  
• Ovarian tumors of low malignant potential (LMP tumors). Ovarian epithelial tumors that do not clearly appear as cancerous under a microscope. These tumors are also known as epithelial borderline ovarian cancer. LMP tumors differ from normal ovarian cancers because they do not grow into the tissue that supports the ovary. LMP tumors tend to be less invasive to surrounding areas and affect women at a younger age. These tumors grow slowly and are less life-threatening than other forms of ovarian cancer.

Primary peritoneal carcinoma, also called extraovarian primary peritoneal carcinoma (EOPPC), is a type of cancer closely related to epithelial ovarian cancer. Primary peritoneal carcinoma originates in cells from the peritoneum, the membrane lining the organs and walls of the pelvis and abdomen. These cells resemble the epithelial cells that coat the surface of the ovaries. Because this condition usually spreads along the surfaces of the abdomen and pelvis, it is normally difficult to determine exactly where the cancer started. EOPPC looks the same as epithelial ovarian cancer when examined under a microscope. Women who have had their ovaries removed can still develop this form of cancer.