Ovarian cancer begins in the ovaries. Women have 2 ovaries, one on each side of the uterus in the pelvis, as shown in the picture below. The ovaries produce eggs (called ova). They are also the main source of a woman's female hormones, estrogen and progesterone. The eggs travel through the fallopian tubes to the uterus. Here they may be fertilized and develop into a fetus.
Many types of tumors can start in the ovaries. Some are benign (not cancer) and never spread beyond the ovary. Women with these types of tumors can be treated by taking out either the ovary or the part of the ovary that has the tumor. Other types of tumors are cancerous (or malignant) and can spread to other parts of the body. They need more treatment which we will explain later.
As a rule, tumors in the ovary are named for the kinds of cells the tumor started from and whether the tumor is benign or cancerous. There are 3 main types of tumors:
Epithelial tumors: These tumors start from the cells that cover the outer surface of the ovary. Most ovarian tumors are epithelial cell tumors.
Germ cell tumors: These start from the cells that produce the eggs.
Stromal tumors: These start from cells that hold the ovary together and make the female hormones.
Treatment is based on the type of tumor, and in many cases a combination of treatments is used. The effectiveness of the treatment depends on the number of factors including the type, size and location of the tumor.
http://www.cancer.org/Cancer/OvarianCancer/OverviewGuide/index