What are ovarian cancer stages?

To understand ovarian cancer staging, it helps to know a little about a woman's anatomy, as well as the different types of ovarian cancer.

Ovarian cancer is a group of diseases that originate in the ovaries, fallopian tubes or the peritoneum (tissue that lines the abdominal wall and organs). Women have two ovaries located in their lower abdomen, on each side of their pelvis. About the size and shape of an almond, the ovaries produce a woman's eggs and female hormones. Eggs pass from the ovaries through long, slender tubes called the fallopian tubes to the uterus. A tissue called the peritoneum covers these structures, and all of these structures reside in the peritoneal cavity, which is inside your abdomen. Ovarian cancer can begin in any of these areas. But wherever it begins, treatment for ovarian cancer works best when the cancer is found early through screening.

The system most often used for staging ovarian cancer is the tumor-node-metastasis (TNM) and International Federation of Gynecology and Obstetrics (FIGO) system, which is based on three key pieces of information:

• T: The extent and size of the tumor
• N: The number of lymph nodes affected
• M: Signs indicating if the cancer has metastasized (spread) to other organs

Numbers or letters after T, N and M provide more details about each of these factors, with higher numbers meaning that the cancer is more advanced. Once this information is known, your healthcare provider combines these values to assign an overall clinical stage.

There are four stages of ovarian cancer: Stage I (early disease) to Stage IV (advanced disease). The treatment plan and outlook for recovery are determined by the stage of the cancer and if it has become metastatic ovarian cancer. Each stage is further defined by the tumor's progression. These are outlined below.

In Stage I, cancer is found in one or both ovaries or fallopian tubes:

• Stage IA: Cancer is found inside one ovary or fallopian tube but not its outer surface
• Stage IB: Cancer is found inside both ovaries or fallopian tubes but not on their outer surfaces
• Stage IC: Cancer is found inside one or both ovaries or fallopian tubes, and one of the following is true:
  • Cancer is also found on the outside surface of one or both ovaries or fallopian tubes
  • The outer covering of the ovary broke open before or during surgery
  • Cancer cells are found in the fluid in the peritoneal cavity

In Stage II, the cancer has extended to the pelvis:

• Stage IIA: Cancer has spread from where it first formed to the uterus, fallopian tubes or the ovaries
• Stage IIB: Cancer has spread from the ovary or fallopian tube to organs in the peritoneal cavity

In Stage III, the cancer has spread beyond the pelvis:

• Stage IIIA: Cancer is found in one or both ovaries or fallopian tubes, and one of the following is true:
  • Cancer has spread to lymph nodes in the area outside or behind the peritoneum only
  • Cancer cells have spread to the omentum, which is a fatty sheet that covers the inside of the abdomen. Cancer may also have spread to nearby lymph nodes.
• Stage IIIB: Cancer is found in one or both ovaries or fallopian tubes and has spread to the omentum, and the cancer in the omentum is 2 centimeters or smaller. Cancer may have spread to lymph nodes as well.
• Stage IIIC: Cancer is found in one or both ovaries or fallopian tubes, has spread to the omentum and is larger than 2 centimeters in the omentum. Cancer may have spread to lymph nodes behind the peritoneum or to the surface of the liver or spleen.

In Stage IV, cancer has spread throughout the body:

• Stage IVA: Cancer cells are found in fluid that builds up around the lungs
• Stage IVB: Cancer has spread to inside the spleen or liver and/or other organs and tissues outside the abdomen, including lymph nodes in the groin

In most cases, chemotherapy is given after surgery for ovarian cancer. Sometimes, it is also given before surgery to reduce the size of the tumor and improve the chances that the surgeon will be able to remove all of the cancer.

Whatever the stage of cancer, your healthcare team will follow you for at least five years after you've completed therapy. During this time, they'll continue to check you periodically to determine if there is any evidence of new or recurring cancers.

 Published February 2020. Clinically reviewed and updated by Julie McDaniel, MSN, RN, CRNI, October 2022.