The ovaries are a pair of female reproductive glands in which eggs are formed. They are located in the pelvis, one on each side of the uterus. The ovaries are composed of three distinct cell types: epithelial cells, germ cells, and stromal cells. Each of these cell types can give rise to different kinds of tumors.
Ovarian cancer is the second most common type of gynecologic cancer. Of the different types of ovarian cancer, epithelial ovarian cancer is the most common, originating in the epithelial cells that cover the surface of the ovary. Other rarer kinds of ovarian cancer include germ cell and stromal cell tumors.
Nine out of ten ovarian tumors originate in the epithelial cells. The American Cancer Society estimates that about 21,550 women in the US will be diagnosed with epithelial ovarian cancer in 2009. Although approximately 14,600 women die from this disease each year in the US, the survival rate of women with ovarian cancer has been increasing over the past three decades.
Germ Cell & Stromal Cell Tumors
Ovarian germ cell tumors start in the cells that produce individual eggs. Germ cell tumors are rare (accounting for one in 20 ovarian tumors), usually occurring in women younger than 20 years. Many germ cell tumors are noncancerous.
Stromal cell tumors start in the supporting connective tissue that holds the ovary together. The female hormones estrogen and progesterone are made in the stromal cells. These tumors can occur in women of any age, but they are also uncommon.