Stage I - Cancer is limited to one or both ovaries.

• IA - Cancer is limited to one ovary and the tumor is confined to the inside of the ovary. (No cancer exists on the outer surface of the ovary.) There is no ascites (the condition of pathologic fluid accumulation within the abdominal cavity) present containing malignant cells. The surface of the tumor is unruptured.
• IB - Cancer is limited to both ovaries without any tumor on their outer surfaces. There is no ascites present containing malignant cells. The surface of the tumor is unruptured.
• IC - The tumor is classified as either Stage IA or IB and one or more of the following conditions exist:
  • A tumor is present on the outer surface of one or both ovaries.
  • At least one of the tumors has ruptured.
  • There are ascites present or abdominal (peritoneal) washings containing malignant cells.

Stage II - The tumor involves one or both ovaries with extension to other pelvic structures.

• IIA - The cancer has extended to and/or involves the uterus or the fallopian tubes or both.
• IIB - The cancer has extended to the bladder or rectum.
• IIC - The tumor is classified as either Stage IIA or IIB and one or more of the following are present:
  • A tumor is present on the outer surface of one or both ovaries.
  • At least one of the tumors has ruptured.
  • There are ascites containing malignant cells or with abdominal (peritoneal) washings containing malignant cells.

Stage III- The tumor involves one or both ovaries, and one or both of the following exist:

• The cancer has spread beyond the pelvis to the lining of the abdomen.
• The cancer has spread to the lymph nodes.
• The tumor is limited to the true pelvis but with histologically proven malignant extension to the small bowel or omentum (peritoneal fold).
• IIIA - During the staging operation, the practitioner can see cancer involving one or both of the ovaries, but no cancer is grossly visible in the abdomen and it has not spread to the lymph nodes. However, biopsies checked under a microscope show tiny deposits of cancer in the abdominal (peritoneal) surfaces.
• IIIB - The tumor is in one or both ovaries, and deposits of cancer are present in the abdomen that are large enough for the surgeon to see but not exceeding 2 cm in diameter. The cancer has not spread to the lymph nodes.
• IIIC - The tumor can be seen in one or both ovaries, and one or both of the following is present:
• the cancer has spread to lymph nodes
• The deposits of cancer exceed two centimeters in diameter and are found in the abdomen.

Stage IV - Growth of the cancer involves one or both ovaries and distant metastases to the liver or lungs have occurred. Finding ovarian cancer cells in the excess fluid accumulated around the lungs (pleural fluid) also shows evidence of stage IV disease. The stage of ovarian cancer at diagnosis is the most important indicator of prognosis (prediction of duration, course and outcome of the disease).