The ovaries and fallopian tubes are part of the female reproductive system. There is one ovary and one fallopian tube on each side of the uterus (the hollow, pear-shaped organ where a fetus grows). The ovaries store eggs and make female hormones. Eggs pass from the ovaries, through the fallopian tubes, to the uterus. The peritoneum is the tissue that lines the abdomen wall and covers organs in the abdomen. Part of the peritoneum is close to the ovaries and fallopian tubes.

The most common type of ovarian cancer is called ovarian epithelial cancer. It begins in the tissue that covers the ovaries. Cancer sometimes begins at the end of the fallopian tube near the ovary and spreads to the ovary. Cancer can also begin in the peritoneum and spread to the ovary. The stages and treatment are the same for ovarian epithelial, fallopian tube, and primary peritoneal cancers.

Another type of ovarian cancer is ovarian germ cell tumor, which is much less common. It begins in the germ (egg) cells in the ovary. Ovarian low malignant potential tumor (OLMPT) is a type of ovarian disease in which abnormal cells form in the tissue that covers the ovaries. OLMPT rarely becomes cancer.

Cancers of the ovaries, fallopian tubes, and primary peritoneum are the fifth leading cause of cancer death in women in the U.S. These cancers are often found at advanced stages. This is partly because they may not cause early signs or symptoms and there are no good screening tests for them.