Ovarian cancer is a cancerous growth arising from different parts of the ovary.
Most (>90%) ovarian cancers are classified as "epithelial" and were believed to arise from the surface (epithelium) of the ovary. However, recent evidence suggests that the Fallopian tube could also be the source of some ovarian cancers. Since the ovaries and tubes are closely related to each other, it is hypothesized that these cells can mimic ovarian cancer. Other types arise from the egg cells (germ cell tumor) or supporting cells (sex cord/stromal).