Stage and grade of ovarian cancer

The staging system for ovarian cancer looks at the size of the tumor, whether the tumor has grown into other tissues, whether the lymph nodes have cancer, and whether the cancer has spread (metastasized) to other areas of the body. Staging of ovarian cancer is done with surgery and has been classified by the American Joint Committee on Cancer (AJCC) and the Fédération Internationale de Gynécologie et d'Obstétrique (FIGO, also called the International Federation of Gynecology and Obstetrics). The two classification systems are very similar.

There are three types of ovarian cancer. The type is determined by the location in the ovary where the cancer develops. These three types are:¹

• Epithelial cancer, which develops in the cells on the surface of the ovary. This is the most common form of ovarian cancer, accounting for about 90% of all ovarian cancers.
• Stromal cell cancer, which develops in the deeper supportive tissue of the ovary. Stromal cell cancer is present in 5% to 8% of all ovarian cancers.
• Germ cell cancer, which develops in an egg cell produced in the ovary. Germ cell cancer is present in less than 5% of all ovarian cancers and most typically occurs in girls and young women.

AJCC TNM and FIGO staging classification²

The primary tumor (T) is staged in the following way with the AJCC classification first and the FIGO stage in parentheses:

• TX. Primary tumor cannot be assessed.
• T0. No primary tumor is seen.
• T1 (Stage I). Ovarian cancer (carcinoma) is limited to one or both ovaries.
• T1a (Stage IA). Tumor is limited to one ovary. The ovarian capsule is intact and there is no tumor on the surface of the ovary. There are no cancer cells in the body fluid (peritoneal fluid) around the ovary.
• T1b (Stage IB). Tumor is limited to both ovaries. The ovarian capsule is intact and there is no tumor on the surface of the ovaries. There are no cancer cells in the body fluid (peritoneal fluid) around the ovaries.
• T1c (Stage IC). Tumor is limited to one or both ovaries AND the ovarian capsule is ruptured or there is tumor on the surface of the ovaries or there are cancer cells in the body fluid (peritoneal fluid) around the ovaries.
• T2 (Stage II). Tumor involves one or both ovaries and extends into the pelvis or has implanted into the uterus.
• T2a (Stage IIA). Tumor has extended or implanted into the uterus or fallopian tube but there are no cancer cells in the body fluid (peritoneal fluid) around the ovaries.
• T2b (Stage IIB). Tumor has extended or implanted into other pelvic tissues but there are no cancer cells in the body fluid (peritoneal fluid) around the ovaries.
• T2c (Stage IIC). Tumor has extended or implanted into other pelvic tissues (T2a or T2b) AND there are cancer cells in the body fluid (peritoneal fluid) around the ovaries.
• T3 (Stage III). Tumor involves one or both ovaries and there are cancer cells outside the pelvis (peritoneal metastasis).
• T3a (Stage IIIA). Cancer cells are identified microscopically outside the pelvis (peritoneal metastasis) or on abdominal peritoneal surfaces.
• T3b (Stage IIIB). Tumor involves one or both ovaries and implants on abdominal peritoneal surfaces measure 2cm or less in size.
• T3c (Stage IIIC). Tumor implants on abdominal peritoneal surfaces measure larger than 2cm in size and/or cancer involves lymph nodes in the abdominal area.

After the tumor (T) is staged, the TNM system stages lymph node involvement (N) to help determine the treatment options at each stage. Lymph node involvement is staged in the following way:

• NX. Lymph nodes near the primary tumor cannot be evaluated.
• N0. Cancer has not spread to lymph nodes near the primary tumor.
• N1. Cancer has spread to lymph nodes near the primary tumor.

The last part of staging ovarian cancer is to determine whether cancer has spread (metastasized) to other parts of the body. The TNM system stages metastasis (M) in the following way:

• MX. Distant metastasis cannot be assessed.
• M0. No distant metastasis is found.
• M1. Metastasis to another part of the body has occurred.

The TNM staging system allows a health professional to recommend the most effective treatment options and discuss the long-term outcome (prognosis) based on the type of tumor, the stage of the cancer, and your age and overall health condition.

The FIGO stages and the AJCC TNM class are grouped in the following table.

Stages and classes of ovarian cancer

FIGO stage	TNM class
Stage I Stage IA Stage IB Stage IC	T1N0M0 T1aN0M0 T1bN0M0 T1cN0M0
Stage II Stage IIA Stage IIB Stage IIC	T2N0M0 T2aN0M0 T2bN0M0 T2cN0M0
Stage III Stage IIIA Stage IIIB Stage IIIC	T3N0M0 T3aN0M0 T3bN0M0 T3cN0M0 Any T, N1, M0
Stage IV	Any T, any N, M1

Grade of ovarian tumors

The grade of ovarian cancer refers to how the cancer cells look under a microscope. Most descriptions of ovarian cancer cells describe them as well-differentiated, moderately differentiated, or poorly differentiated. Differentiation is a term used to describe how clearly the cancer cells can be distinguished from the surrounding healthy tissues and how normal or abnormal the cells look.

• Well-differentiated cancers have very clear boundaries and cells that look relatively normal. They usually do not grow or spread rapidly.
• Poorly differentiated cancers have less clearly defined boundaries and cells that look very abnormal. They often grow and spread rapidly.

Ovarian tumors are evaluated in the following grades:

• GX: Grade cannot be assessed
• GB: Borderline cancer (malignant)
• G1: Well-differentiated cancer
• G2: Moderately differentiated cancer
• G3–G4: Poorly differentiated or undifferentiated cancer

Citations

1. Berek JS (2002). Ovarian cancer. In JS Berek, ed., Novak's Gynecology, 13th ed., pp. 1245–1319. Philadelphia: Lippincott Williams and Wilkins.

2. American Joint Committee on Cancer (2002). Ovary. In AJCC Cancer Staging Manual, 6th ed., pp. 275–279. New York: Springer-Verlag.