About the ovaries
The ovaries are glands that contain the germ cells, also called eggs. Every woman has two ovaries as part of her reproductive system, one located on each side of the uterus. They are almond shaped and about one and a half inches long. Every month, during ovulation, an egg is released from an ovary and travels to the uterus through a structure called the fallopian tube.
Ovaries are the primary source of estrogen and progesterone. These hormones influence breast growth, body shape, body hair, and regulate the menstrual cycle and pregnancy. During menopause, the ovaries stop releasing eggs and producing certain hormones.
About ovarian cancer
Ovarian cancer begins when healthy cells in an ovary change and grow uncontrollably, forming a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A benign tumor means the tumor can grow but will not spread. Removing the ovary or the part of the ovary where the tumor is located can treat a noncancerous ovarian tumor. An ovarian cyst, which forms on the surface of the ovary, is different than a noncancerous tumor and usually goes away without treatment. A simple ovarian cyst is not cancerous. They often occur during the normal menstrual cycle.
Types of ovarian cancer include:
Epithelial carcinoma. Epithelial carcinoma makes up 85% to 90% of ovarian cancers. While historically considered to start on the surface of the ovary, new evidence suggests at least some ovarian cancer begins in special cells in a part of the fallopian tube. The fallopian tubes are small ducts that link a woman’s ovaries to her uterus that are a part of a woman’s reproductive system. Every woman has two fallopian tubes, one located on each side of the uterus. Cancer cells that begin in the fallopian tube may go to the surface of the ovary early on. The term 'ovarian cancer' is often used to describe epithelial cancers that begin in the ovary, in the fallopian tube, and from the lining of the abdominal cavity, call the peritoneum.
The majority of patients with epithelial ovarian cancer have a histologic type of cells called “high grade serous carcinoma.” See the Latest Research section for specific information regarding targeted therapies being developed for the less common “low grade serous carcinoma.” Most of the Treatment Options described in this guide apply to epithelial ovarian cancer.
Germ cell tumor. This uncommon type of ovarian cancer develops in the egg-producing cells of the ovaries. This type of tumor is more common in females ages 10 to 29.
Stromal tumor. This rare form of ovarian cancer develops in the connective tissue cells that hold the ovaries together, which sometimes is the tissue that makes female hormones called estrogen. Over 90% of these tumors are adult or childhood granulosa cell tumors. Granulosa cell tumors may secrete estrogen resulting in unusual vaginal bleeding at the time of diagnosis.
Looking for More of an Overview?
If you would like additional introductory information, explore these related items. Please note these links will take you to other sections on Cancer.Net:
- ASCO Answers Fact Sheet: Read a one-page fact sheet (available as a PDF) that offers an easy-to-print introduction to this type of cancer.
- Cancer.Net En Español: Read about ovarian cancer in Spanish. Infórmase sobre cáncer de ovario en español.
- Cancer.Net Videos: Watch this introduction to ovarian cancer. In addition, learn more about sexual health and cancer.