Cancer is a disease in which some of the body’s cells begin to divide without stopping, and spread into surrounding tissue. Ovarian cancers are a group of diseases that affect a woman’s ovaries.

There are several types of ovarian cancer. While these diseases are all called “ovarian” because they affect the ovaries, they are actually unique in terms of their origin, how they look under a microscope, treatment and prognosis.

Ovarian tumors can be benign (noncancerous) or malignant (cancerous). Although abnormal, cells of benign tumors do not metastasize (spread to other parts of the body).

Additionally, ovarian cysts are different than ovarian tumors, and can be fairly common—ovarian cysts are fluid-filled while ovarian tumors are solid masses. Most ovarian cysts are not harmful, don’t cause symptoms and are not indicative of risk for future ovarian cancer, though some complex ovarian cysts may raise the risk.

The ovaries are a pair of organs in the female reproductive system. They are in the pelvis, one on each side of the uterus (the hollow, pear-shaped organ where a fetus grows). Each ovary is about the size and shape of an almond. The ovaries make eggs and female hormones.  The fallopian tubes are a pair of tubes through which eggs travel from the ovaries to the uterus. The peritoneum is the membrane lining the cavity of the abdomen and covering the abdominal organs.

Types of Ovarian Cancer

Ovarian cancers are now known to be several distinct diseases, which are named after the type of cell they come from: epithelial, germ cell, and stromal.  These are the three main cell types that make up the ovary.  Each cell type can develop into a different type of tumor, and each type differs in how it spreads, how it’s treated and its prognosis.

Not all ovarian tumors are cancer. Some ovarian tumors may be abnormal but not necessarily cancerous.

• Epithelial ovarian cancer, which arise from the surface of the ovary (the epithelium), is the most common ovarian cancer. Fallopian Tube Cancer and Primary Peritoneal Cancer are also included within this designation.
• Germ Cell ovarian cancer arises from the reproductive cells of the ovaries, and is rare.
• Stromal cell ovarian cancer, which arises from connective tissue cells, is very rare.
• Small cell carcinoma (SCCO) of the ovary is an extremely rare ovarian cancer and it is not certain whether the cells in SCCO are from ovarian epithelial cells, sex-cord stromal cells or germ cells.

Staging and Grading

Staging is the process of finding out how much cancer is in a person’s body and where it’s located. It’s how the doctor determines the stage of a person’s cancer. For most types of cancer, doctors use staging information to help plan treatment and to predict a person’s outlook (prognosis). Although each person’s situation is different, cancers with the same stage tend to have similar outlooks and are often treated the same way. The cancer stage is also a way for doctors to describe the extent of the cancer when they talk with each other about a person’s cancer.

Each of these stages, except Stage IV, is divided into A, B, and C.

Stage I – Cancer is found in one or both ovaries:

IA – Cancer is found inside a single ovary.

IB –  Cancer is found inside both ovaries.

IC –  Cancer is found inside one or both ovaries and one of the following is true:

• cancer is also found on the outside surface of one or both ovaries; or
• the capsule (outer covering) of the ovary has ruptured (broken open); or
• cancer cells are found in the fluid of the peritoneal cavity (the body cavity that contains most of the organs in the abdomen) or in washings of the peritoneum (tissue lining the peritoneal cavity).

Stage II – Cancer is found in one or both ovaries and has spread into other areas of the pelvis.

IIA – Cancer has spread to the uterus and/or fallopian tubes (the long slender tubes through which eggs pass from the ovaries to the uterus).

IIB – Cancer has spread to other tissue within the pelvis.

IIC – Cancer is found inside one or both ovaries and has spread to the uterus and/or fallopian tubes, or to other tissue within the pelvis. Also, one of the following is true:

• cancer is found on the outside surface of one or both ovaries; or
• the capsule( outer covering) of the ovary has ruptured (broken open); or
• cancer cells are found in the fluid of the peritoneal cavity (the body cavity that contains most of the organs in the abdomen) or in washings of the peritoneum (tissue lining the peritoneal cavity).

Stage III – Cancer is found in one or both ovaries and has spread outside the pelvis to other parts of the abdomen and/or nearby lymph nodes. Cancer that has spread to the surface of the liver is also considered stage III ovarian cancer.

IIIA – The tumor is found in the pelvis only, but cancer cells that can be seen only with a microscope have spread to the surface of the peritoneum (tissue that lines the abdominal wall and covers most of the organs in the abdomen), the small intestines, or the tissue that connects the small intestines to the wall of the abdomen.

IIIB – Cancer has spread to the peritoneum and the cancer in the peritoneum is 2 centimeters or smaller.

IIIC – Cancer has spread to the peritoneum and the cancer in the peritoneum is larger than 2 centimeters and/or cancer has spread to lymph nodes in the abdomen.

Stage IV –  In stage IV, cancer has spread beyond the abdomen to other parts of the body, such as the lungs or tissue inside the liver.  Cancer cells in the fluid around the lungs is also considered stage IV ovarian cancer.

The stage of ovarian cancer at diagnosis is also the most important indicator of prognosis (prediction of duration, course and outcome of the disease.)

Grading

By looking at the cells in the tissue and fluid under a microscope, a pathologist describes the cancer as Grade 1, 2, or 3.

Grade 1 is most like ovarian tissue and less likely to spread; Grade 3 cells are more irregular and more likely to metastasize.

However, many ovarian cancers are categorized simply as “low grade” or “high grade.” Chemotherapy is often not used to treat low grade Stage I cases.

This information has been taken with permission from the Ovarian Cancer Research Alliance, https://ocrahope.org/