Once ovarian cancer is diagnosed, it is graded and staged. The grade describes how the cancer cells look under a microscope, and the stage describes the size of the tumor and how widely it has spread. Both grading and staging can help an oncologist predict a person’s outcome and decide which treatment options may be best.

Ovarian Cancer Grades

A tumor’s grade describes whether its cells look more healthy or more abnormal. Healthy cells that are fully mature and have a specialized role in the body are described as “differentiated.” Abnormal cells that are immature, such as many cancer cells, are described as “undifferentiated.” To assess tumor grade, a doctor will take a tissue sample of the tumor and view the cells under a microscope. The doctor will then judge how differentiated the cells look and assign a grade:

• Grade 1 — Cells are differentiated and mostly look like normal ovarian cells.
• Grade 2 — Cells are somewhat differentiated, and there is a mixture of healthy and unusual-looking cells.
• Grade 3 or 4 — Cells look mostly undifferentiated and abnormal.

Some types of ovarian cancer may not receive a grade. For example, in serous carcinoma of the ovary (a type of epithelial ovarian cancer), tumors are classified as either high-grade or low-grade rather than receiving a number. Other tumors are simply graded as borderline cancerous, which means they have low malignant potential. These tumors usually don’t spread and aren’t as harmful.

Ovarian Cancer Stages

A cancer’s stage describes how much it has spread and where it is located in the body. To determine cancer stage, a doctor will generally use a process called surgical staging or pathological staging. In this case, a doctor will examine cancer tissue during and after surgery, as the tumor is removed. If someone isn’t able to have surgery, doctors may assign a stage based on a physical exam, imaging such as a CT scan, or a biopsy. This is called clinical staging.

There are a couple of ways to describe a tumor’s stage. The FIGO staging system was developed by the International Federation of Gynecology and Obstetrics. It uses a series of letters and Roman numerals, ranging from stage I (stage 1, least severe) to stage IV (stage 4, most severe).

The other staging system is called TNM staging and was created by the American Joint Committee on Cancer. It uses the letters T, N, and M to describe different characteristics of the cancer.

• T stands for tumor, and describes the size of the main tumor. A tumor may be staged as T1, T2, T3, or T4, with larger numbers corresponding to larger tumors. Cancers are also further classified with letters such as T1A or T1B to give more information.
• N describes whether the cancer has spread to nearby lymph nodes. Lymph nodes are glands that filter out harmful substances. Cancer cells may appear in the lymph nodes once they start to spread. A tumor is staged as N0 if there are no cancer cells in nearby lymph nodes, or as N1, N2, or N3 depending on how many lymph nodes have cancer.
• M stands for metastasis, which is the scientific term for the spread of cancer from the tumor to other parts of the body. M0 tumors have not spread, while M1 tumors have begun to metastasize.

Doctors may describe a tumor using either or both of these systems. Both systems mean essentially the same thing. Peritoneal (the lining of the abdomen) and fallopian tube cancers are also staged using these systems, since these cancer types are similar.

Stage 1 Ovarian Cancer

In stage 1 ovarian cancer, there is a tumor in one or both ovaries or fallopian tubes. This stage of cancer can also be described as T1-N0-M0, meaning there is a small tumor, there are no cancer cells in the lymph nodes, and the tumor has not metastasized. Stage 1 ovarian cancer can be further divided into substages to provide more detail:

• Stage IA (T1A-N0-M0) — Only one ovary or one fallopian tube has cancer. The cancer is only on the inside, not the outside, of the ovary or fallopian tube. No cancer cells can be found in other parts of the body.
• Stage IB (T1B-N0-M0) — Both ovaries or both fallopian tubes have cancer. The cancer is only on the inside, not the outside, of the organs. No cancer cells can be found in other places.
• Stage IC (T1C-N0-M0) — One or both ovaries or fallopian tubes have cancer, and cancer can’t be found elsewhere in the body. This stage is also further broken down based on other features that are present. In stage IC1, the tissue near the tumor broke open during surgery, which may lead to cancer cells escaping into the body. In stage IC2, either the tissue near the tumor broke open before surgery happened, or there is cancer on the outside of the ovary or fallopian tube. In stage IC3, cancer cells are found in fluid inside the abdomen or belly.

Stage 2 Ovarian Cancer

In stage 2 ovarian cancer, there is a tumor in one or both ovaries or fallopian tubes. Cancer has also started spreading to nearby organs, such as the bladder or uterus. There is no spread of cancer cells to lymph nodes or to other locations in the body. This stage may also be written as T2-N0-M0. Stage 2 disease can be further divided as:

• Stage IIA (T2A-N0-M0) — Cancer has spread from the ovary to the fallopian tube, or vice versa, or cancer has spread to the uterus. There is no cancer in other places in the body.
• Stage IIB (T2B-N0-M0) — Cancer has spread to other organs nearby, including the bladder, colon, or rectum. There is no cancer in lymph nodes or more distant locations.

Read more about stage 2 ovarian cancer.

Stage 3 Ovarian Cancer

People with stage 3 ovarian cancer have tumors that have spread outside of the pelvic area. People may also be diagnosed with stage 3 cancer if cancer cells have spread to lymph nodes nearby in the abdomen or if they have a tumor that came from the peritoneum (tissue that lines the abdominal wall and covers most pelvic organs). Stage 3 ovarian cancer may be subdivided as:

• Stage IIIA1 (T1-N1-M0 or T2-N1-M0) — One or both ovaries or fallopian tubes has cancer. Cancer is found in nearby lymph nodes, but the tumor has not metastasized.
• Stage IIIA2 (T3A-N0-M0 or T3A-N1-M0) — One or both ovaries or fallopian tubes has cancer, and it has spread outside of the pelvic area. There are no metastases, but there may be cancer in the nearby lymph nodes. If someone was diagnosed with stage IIIA2, that also means that doctors could not see any cancer in the peritoneum during surgery, but when they later looked at the tissue under a microscope, they found some cancer cells.
• Stage IIIB (T3B-N0-M0 or T3B-N1-M0) — Cancer has spread from the ovaries or fallopian tubes to other places inside the abdomen, but the new tumors are small. People with or without cancer cells in the lymph nodes are included in this category. There is no spread of cancer to more distant organs.
• Stage IIIC (T3C-N0-M0 or T3C-N1-M0) — Cancer has spread from the ovaries or fallopian tubes to other places in the abdomen, such as the outside of the liver or spleen, and the tumors are medium or large. There may be spread of cancer cells to lymph nodes, but not to farther locations.

Read more about stage 3 ovarian cancer.

Stage 4 Ovarian Cancer

Stage 4 ovarian cancer may also be called advanced stage or late stage ovarian cancer. It occurs when tumors have spread throughout the body. Cancer is found in other organs or locations far away from the ovaries. There are two subcategories of stage 4 ovarian cancer:

• Stage IVA (Any T- Any N- M1A): There are cancer cells in the fluid that surrounds the lungs.
• Stage IVB (Any T-Any N-M1B): Cancer is found inside the spleen or liver, in organs that are farther away such as lungs or bones, or in distant lymph nodes.

Read more about stage 4 ovarian cancer.

How Are Grades and Stages Used?

The oncologist will use grading and staging for several purposes. This information can help a doctor estimate a person’s prognosis or estimate how the cancer will progress. It can also help the doctor know which cancer treatment plan will be most helpful. Lower-grade and lower-stage tumors are generally less severe, indicate a better disease outlook, and can be more easily treated.

Higher-grade or higher-stage tumors may be more likely to spread and need a more aggressive treatment plan. They generally have lower survival rates. However, some ovarian tumors may be treated differently even when they are at the same stage. An oncologist will also take other factors into consideration, such as the ovarian cancer type or certain characteristics of the person who has cancer.

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