The stage of a cancer is a term used to describe its size and whether it has spread beyond its original area of the body. Knowing the extent of the cancer and the grade helps the doctors to decide on the most appropriate treatment. It’s often not possible to stage an ovarian cancer before a laparotomy is done and the results of any biopsies are known (see diagnosis). A commonly used staging system is described below.

Borderline tumours are made up of low-grade cells that are unlikely to spread. They are usually completely cured by surgery and rarely require further treatment.

Stage 1 ovarian cancer only affects the ovaries. This stage is divided into three sub-groups:

• Stage 1a The cancer is only in one ovary
• Stage 1b There are tumours in both ovaries.
• Stage 1c The cancer is either at stage 1a or 1b, and there are cancer cells on the surface of one of the ovaries, or in the fluid taken from within the abdomen during surgery, or the ovary has burst (ruptured) before or during surgery.

Stage 2 ovarian cancer has begun to spread outside the ovaries within the pelvis. There are three sub-groups:

• Stage 2a The cancer has spread to the womb or fallopian tubes.
• Stage 2b The tumour has spread to other structures within the pelvis, such as the rectum or bladder.
• Stage 2c The cancer is either at stage 2a or 2b, and there are cancer cells on the surface of one of the ovaries, or in the fluid taken from within the abdomen during surgery, or the ovary has burst (ruptured) before or during surgery.

Stage 3 The cancer has spread beyond the pelvis to the lining of the abdomen (a fatty membrane called the omentum), and/or to abdominal organs such as the lymph nodes in the abdomen, or the upper part of the bowel.

• Stage 3a The tumours in the abdomen are very small and cannot be seen except under a microscope.
• Stage 3b The tumours in the abdomen can be seen but they are smaller than 2cm.
• Stage 3c The tumours in the abdomen are larger than 2cm.

Stage 4 The cancer has spread to other parts of the body such as the liver, lungs, or distant lymph nodes (for example in the neck).

If the cancer comes back after initial treatment this is known as recurrent cancer.

Grading refers to the appearance of the cancer cells when they are looked at under the microscope. The grade gives an idea of how quickly the cancer may develop. There are three grades: grade 1 (low-grade), grade 2 (moderate-grade) and grade 3 (high-grade).

• Low-grade means that the cancer cells look very like the normal cells of the ovary. They usually grow slowly and are less likely to spread.

• Moderate-grade means that the cells look more abnormal than low-grade cells.

• High-grade means that the cells look very abnormal. They are likely to grow more quickly and are more likely to spread.