Ovarian cancer occurs when part of the normal cells of the ovaries begin to transform and divide in an uncontrolled manner to become malignant. In some women, this division does not lead to a malignant tumor; their immune system fights the disease and prevents the cancer from developing. For others, however, their immune system is not able to destroy those belligerent cells; their numbers continue to increase to form a malignant tumor. The tumor is initially well defined; it produces no symptoms. Over time, however, cancer cells invade surrounding tissue to destroy them gradually. Cancer cells can also use the lymphatic system or bloodstream to reach parts of the body far distant from their point of departure to form new tumors; this condition is called metastatic ovarian cancer.
Scientists do not know for sure the causes of ovarian cancer; there are however, many suspected factors. Although it exists many, the only risk factor to develop cancer of the ovary clearly highlighted is family history of the cancer. In most families, the increased risk is due to genetic predisposition to ovarian cancer.