What Is Ovarian Cancer?

According to the U.S. Centers for Disease Control and Prevention (CDC), ovarian cancer is the fifth leading cause of cancer death among females, after lung, breast, colorectal, and pancreatic cancers. It is also the leading cause of death among cancers of the female reproductive system. In 2023, it accounts for just over 2 percent of all cancers in females, according to the American Cancer Society. No one knows the exact cause of ovarian cancer. However, most cases are linked to a defect of one or more genes. Cancer occurs when cells grow out of control. This results in masses of cells called tumors, which can damage surrounding tissue.

Ovarian cancer is more common in industrialized nations. It affects about 1 out of every 78 females. Although some cases occur in young females, the majority of cases occur in females between the ages of 40 and 79. It occurs more frequently as females age. Even if it does not affect you directly, it might affect someone in your family.

Ovarian cancer is cancer that originates in the ovaries. However, it can spread from the ovaries to other parts of the reproductive system and beyond. In order to understand ovarian cancer, it is first necessary to know something about the female reproductive system.

The Female Reproductive System

Female reproductive system. View Larger Image © Superstock, Inc.

The internal organs of the female reproductive system include the uterus (womb), ovaries, and fallopian tubes. The ovaries, one on each side of the uterus, are about the size and shape of unshelled almonds. They are the organs that produce, store, and release eggs (ova is Latin for “eggs”). Men begin producing sperm at puberty and continue to do so throughout their adult lives. Females, on the other hand, are born with all the eggs they will ever have.

Immature egg cells are called oocytes. After puberty, an oocyte matures and is released from an ovary about once a month. The egg travels from the ovary into the fallopian tube and down toward the uterus. If the egg is fertilized by sperm, then it may implant in the uterus and ultimately develop into a fetus. If it is not fertilized, then it will be expelled from the uterus during menstruation (a female’s period).

An ovary has several layers. The outermost layer of the ovary is made up of epithelial cells. These cells line the inside and outside surfaces of the body and all of its organs. Beneath the ovary’s epithelial layer is a layer of connective tissue, or tissue that supports and connects body parts. Beneath that is the major part of the ovary, the cortex. The cortex is filled with follicles, which are round clusters of cells. Each follicle contains one immature egg. A follicle goes through several stages during which it matures and eventually releases the egg. The innermost layer of the ovary is called the medulla. It contains the tissue that attaches the ovary to the abdominal wall and to the blood vessels that bring nourishment to the cells of the ovary and remove waste.

The Growth of Ovarian Cancer Tumors

Cancer occurs when cells grow out of control. All the cells in the body function for a period, reproduce, and eventually die. New cells then replace the ones that have died. This life cycle of cells is controlled by genes. Some genes cause cells to grow, and other genes cause them to stop growing and eventually die. When something goes wrong with one of these genes, cells may grow unchecked. This is what happens with cancer.

Cancer cells grow rapidly and live longer than normal cells. They also reproduce, making more cancer cells. Eventually, the cells form a solid mass that grows ever larger. This mass of cells is called a tumor. Tumors can be either benign or malignant. Benign tumors grow slowly and do not spread. Malignant tumors, on the other hand, grow quickly and aggressively spread to other organs.

Mass surrounding left ovary. View Larger Image © Nucleus Medical Art, Inc./Phototake

When cancer originates in an ovary, it is called ovarian cancer. As the cancerous cells continue to reproduce and grow, they damage the ovarian tissue around them. Cancer can spread from the ovary to other organs of the reproductive system and to other parts of the body as well. The spreading of cancer to other parts of the body is called metastasis.

History of Cancer

The earliest recorded cases of cancer come from an Egyptian papyrus dating back to 3000–1500 BCE. The text describes the removal of tumors from the breasts of several patients.

The word “cancer” comes from the Greek word karkinos, meaning “crab.” The name was coined by Hippocrates (circa 460–370 BCE), the ancient Greek physician who thought the tumors he saw looked like crabs. The ancients did not know what caused cancer. Ancient Egyptians believed it was visited upon people by the gods. Much later, in medieval times, people believed that health was controlled by four substances that circulated in the body: blood, phlegm, yellow bile, and black bile. They called these substances humors. They believed that disease was caused by an imbalance among the four humors. Medieval doctors believed that cancer was caused by too much black bile building up at a place in the body.

In the 1600s, doctors began to develop a more scientific knowledge of the body and its organs. They discovered the lymph nodes, where immune system cells are made, and they learned that lymphatic fluid circulates throughout the body. They started to understand that there was some relationship between the lymphatic system and disease. However, they did not really know about cells, which cannot be seen by the naked eye. They proposed that cancer was caused by lymph fluid collecting and fermenting, or rotting. Several other theories were proposed as causes of cancer, including injury and parasites such as worms.

Discovering Cancer Cells

Microscopes date back to the 1600s. However, it wasn’t until the 1800s that they became powerful enough to allow scientists to use them to study cells. German doctor Rudolph Virchow (1822–1902) observed the difference between normal cells and cancer cells. He also noted the changes that take place in cancer cells over time as symptoms of the disease progress. The most common type of ovarian cancer is epithelial cell cancer. In the late 1800s, a German surgeon named Karl Thiersch (1822–1895) first discovered that epithelial cancer was caused by malignant cells spreading throughout the body.

In 1889, an English surgeon named Stephen Paget proposed the “seed and soil” theory of how cancer is spread. He thought that cancer cells could spread through the body from the original site of the cancer but would only take root in organs that had suitable conditions for them to grow. Modern scientists have confirmed Paget’s basic theory regarding what happens when cancer cells spread from a tumor to other parts of the body. Their ability to grow in the new location does indeed depend on the conditions of the cells in the new environment.

History of Cancer Treatment

Surgery improved greatly during the nineteenth century, especially with the development of better anesthesia (pain numbing) and sterilization techniques. During this time, surgical treatment of most cancers involved removing the tumors and the surrounding tissue. In many cases, this radical (“at the root”) type of surgery prolonged a patient’s life. However, surgery often left the patient deformed and in pain.

Toward the end of the nineteenth century, with increasing knowledge of the way cancer grows and spreads, physicians looked to nonsurgical ways to treat cancer. In 1896, German scientist Wilhelm Conrad Roentgen (1845–1923) invented the X-ray machine. By 1899, X-rays were being used to treat tumors in an early form of radiation therapy.

Chemicals were also used against cancer in a cruder form of modern chemotherapy. The first mention of chemicals being used in this way appears in an 1894 medical textbook by the Canadian physician Sir William Osler (1849–1919). Osler records the use of arsenic to treat cancer.

The development of chemical weapons in World War II (1939–1945) led to major advances in chemotherapy. For example, poisonous mustard gas was used as a weapon because it debilitated and sometimes killed soldiers on the battlefield. While studying the dead bodies of these unfortunate soldiers, doctors discovered that mustard gas actually dissolved lymphatic tissue when inhaled. With this knowledge, researchers Louis S. Goodman and Alfred Gilman pursued the use of mustard gas in treating cancerous tumors. They performed a study using nitrogen mustard, a chemical derived from mustard gas, with very promising results, and the search was on to find ever more effective chemicals for treating a variety of cancers.

In 1961, scientist Barnett Rosenberg (1926–) accidentally discovered that the metal platinum could be used to kill cancer cells. While studying electrical fields, Rosenberg found that bacteria stopped dividing altogether when he put them in an electric field he created. He was surprised to find that the bacteria were not reacting to the electric field but to being exposed to the platinum he had used to make the electric field. Eventually, Rosenberg and his colleagues created the platinum-based compound cisplatin for medical use. In 1978, the U.S. Food and Drug Administration (FDA) approved cisplatin for use in treating solid tumors. Platinum-based compounds are still used to treat ovarian cancer.

In October 2024, researchers at the University of Oxford secured funding to create the world’s first vaccine designed to prevent ovarian cancer. Their research will focus on identifying which proteins on the surface of early-stage ovarian cancer cells are most effectively recognized by the immune system, as well as testing how well the vaccine targets and destroys organoids—mini-models of ovarian cancer. If their research proves successful, the next step will be to initiate clinical trials. The ultimate goal is to offer women a vaccine that could help prevent ovarian cancer before it occurs.