Cancer develops when abnormal cells in a part of the body (in this case, the ovary) begin to grow uncontrollably. This abnormal cell growth is common among all cancer types.
Normally, cells in your body divide and form new cells to replace worn out or dying cells, and to repair injuries. Because cancer cells continue to grow and divide, they are different from normal cells. Instead of dying, they outlive normal cells and continue to create new abnormal cells, forming a tumor. Tumors can put pressure on other organs near the ovaries.
Cancer cells can sometimes travel to other parts of the body, where they begin to grow and replace normal tissue. This process, called metastasis, occurs as the cancer cells move into the bloodstream or lymph system of the body. Cancer cells that spread from other organ sites (such as breast or colon) to the ovary are not considered ovarian cancer. Cancer type is determined by the original site of the malignancy.