Ovarian cancer is the seventh most common cancer in women in the U.S. with over 25,000 women newly diagnosed each year with this disease. It is the fifth leading cause of cancer deaths in women and frequently does not result in symptoms until the cancer has spread extensively. Less than one-third of ovarian cancers are detected before they have spread outside of the ovaries. Ovarian cancer actually represents a group of different tumors that arise from diverse types of tissue contained within the ovary. The most common type of ovarian cancer arises from the epithelial cells (the outside layer of cells ) of the surface of the ovary. Other, rare types of ovarian cancer develop from the egg-forming germ cells or from the supporting tissue (stroma) of the organ. Benign (non-cancerous) tumors and cysts are also found in the ovary and are much more common than ovarian cancers.