Ovarian cancer is a variety of cancer that affects the ovaries which are part of the reproductive organs in a female. There are many types of ovarian cancer but the three most common types are: Epithelial Ovarian Cancer: Epithelial cancer is the most common type of ovarian cancer. It occurs in the epithelial layer of the ovaries and affects the serous tissue. Germ Cell Cancer: Germ cell cancer is the rarest form of ovarian cancer. It occurs in the cells that produce the eggs. Ovarian Stromal Cancer: Stromal cancer is a rare form of ovarian cancer that occurs in the tissue that connects the ovaries.