In women under age 30, most ovarian growths are benign, fluid-filled sacs called cysts. Cysts may occur during a women's monthly cycle and often go away without any treatment. If a cyst does not go away, the doctor may suggest removing it, especially if it is causing problems or seems to be changing. In some cases, the doctor may decide to wait and watch for changes with ultrasonography or other tests. Malignant tumors are cancer.
Cancer cells can invade and damage tissues and organs near the tumor.
Also, cancer cells can break away from a malignant tumor in the ovary and spread to other organs in the abdomen and form new tumors. The cancer cells also can enter the lymphatic system or the bloodstream and spread to other parts of the body. The spread of cancer is called metastasis. There are several types of ovarian cancer. Ovarian tumors are the most histologically diverse group of tumors.