Among the three main types of ovarian cancer, epithelial ovarian cancer is by far the most common type: It represents about 9 of 10 cases of ovarian cancer. In this type of cancer, tumors begin growing in the epithelial cells found on the outer surface of the ovary.

Other types of ovarian cancer are less common. Germ cell tumors affect the egg cells in the ovaries. Stromal tumors develop from the tissue that provides structure for the ovary and makes reproductive hormones. Epithelial ovarian cancers may require different treatments and lead to different outcomes compared to germ cell or stromal cell cancers.

Types of Epithelial Tumors

Experts further divide epithelial tumors into types based on the way the tumors grow and what the cancer cells look like. Not all tumors that develop from epithelial cells are diagnosed as cancer. Some are benign (non-cancerous), and don’t grow out of control like a cancerous tumor would. Others are called “borderline” or “low malignant potential.” These tumors contain cells that grow abnormally, but rarely spread into nearby tissues.

Malignant (cancerous) epithelial tumors contain cells that are very abnormal. They spread throughout the body if left untreated. There are several types of epithelial cancers that grow in the ovary:

• Serous carcinoma — These tumors can be high-grade (fast-growing) or low-grade (slow-growing).
• Endometrioid carcinoma — This cancer usually grows slowly, but it can be difficult to treat. It may arise from endometriosis.
• Mucinous carcinoma — These tumors grow slowly and most often develop in older women.
• Clear cell carcinoma — This cancer is often caught early, which may lead to a better outcome. It may arise from endometriosis.

Cancers of the fallopian tube and peritoneum (inner lining of the abdomen) are often grouped together with epithelial ovarian cancer. These cancers often grow and act in similar ways and are treated with the same treatment plans.

What Causes Epithelial Ovarian Cancer?

Cancers form when a cell develops gene mutations that cause it to grow abnormally. These mutations may make a cell produce new cells too quickly or prevent a cell from healing damage.

Some gene mutations are inherited (passed down within families). They are present at birth in all of a person’s cells. The most commonly mutated genes that can lead to ovarian cancer are BRCA1 and BRCA2. About 10 percent to 15 percent of epithelial ovarian tumors contain BRCA mutations. These mutations can also increase a person’s breast cancer risk. Other cancer-causing gene changes can also be passed down. Overall, up to 1 in 4 people with ovarian cancer have inherited gene mutations. Doctors often recommend genetic testing to look for these mutations.

More often, ovarian cancer is caused by acquired gene changes that develop in a couple of cells during a person’s lifetime. Different environmental or lifestyle-related factors associated with these mutations increase someone’s chances of developing epithelial ovarian cancer.

These risk factors include:

• Older age
• Obesity
• Using hormone replacement therapy during menopause
• Birthing a first child after the age of 35
• Never having birthed children

Some of these risk factors can’t be controlled. However, there are steps a person can take to reduce their ovarian cancer risk. People who breastfeed develop ovarian cancer at lower rates. Additionally, using hormonal birth control methods such as oral contraceptives (birth control pills) or IUDs can lower a person’s risk.

Epithelial Ovarian Cancer Symptoms

Epithelial ovarian cancer may not cause any signs at first. However, as it grows it is more likely to lead to symptoms like:

• Pain in the abdomen, pelvis, or back
• Feeling full after eating a small amount
• Bloating or swelling in the abdomen
• Feeling more frequent or stronger urges to urinate
• Digestive problems such as indigestion or constipation
• A pelvic lump or mass

If you notice any of these symptoms, talk to your health care team.

How Is Epithelial Ovarian Cancer Diagnosed?

Epithelial cancers of the ovary can be diagnosed following a series of tests. If you notice possible symptoms of ovarian cancer, or if your doctor detects potential signs like a lump during a physical exam, your doctor may perform a pelvic exam. Your doctor will examine your vagina, cervix, and the other tissues in the pelvis, and feel for any lumps.

A CA-125 blood test may also detect signs of cancer. The CA-125 molecule is made by cancer cells. High CA-125 levels can be a sign of epithelial ovarian cancer or of other benign conditions, like endometriosis.

Your doctor may want to use imaging tests to get a better look at your reproductive organs. This often includes an ultrasound, which uses sound waves to form images. Some people may need to use another imaging test such as a computed tomography (CT) or magnetic resonance imaging (MRI) scan.

The only way to know for sure whether a mass is cancerous is through a biopsy. During this procedure, a small piece of tissue is removed so that it can be examined under a microscope. Masses on the ovaries or fallopian tubes are usually biopsied during surgery.

Treating Epithelial Ovarian Cancer

Doctors may recommend several different types of treatments for epithelial ovarian cancer, such as surgery, chemotherapy, and targeted therapy. Your treatment plan may depend on the gene changes found in your cancer cells and whether it is possible to surgically remove your cancer, as well as other factors.

Those other factors include your:

• Age
• Overall health
• Subtype of epithelial ovarian cancer
• Cancer stage (how far in the body the cancer has spread)
• Symptoms

Surgery

Epithelial ovarian cancer treatment usually begins with surgery. The surgeon often performs a bilateral salpingo-oophorectomy (removal of the fallopian tubes and ovaries) and hysterectomy (removal of the uterus). These procedures lead to infertility.

Some people with very early-stage ovarian cancer have tumors in only one ovary or fallopian tube. If these individuals want to get pregnant in the future, they may be able to have only the cancer-containing organs removed. If the remaining ovary and fallopian tube and the uterus are left in place, pregnancy may be an option. However, most people with ovarian cancer will need to have all of their reproductive organs removed.

If cancer has begun to spread to nearby tissues, doctors will perform cytoreduction (or debulking) surgery. This procedure involves removing as much cancer as possible. The surgeon may need to remove tumors from multiple areas and take out any tissues that contain cancer cells.

Chemotherapy

Most people with epithelial ovarian cancer need to have six or more rounds of chemotherapy after undergoing surgery. Usually, doctors recommend two chemotherapy drugs: carboplatin (Paraplatin) and paclitaxel (formerly sold under the brand Taxol). Chemotherapy may be intravenous (injected into a vein through an IV) or intraperitoneal (delivered directly into the abdomen).

People with stage 3 or stage 4 epithelial tumors may need to undergo chemotherapy treatments before surgery to shrink the cancer and make it easier to remove. Chemotherapy done in this sequence is called neoadjuvant chemotherapy.

Targeted Therapy

Chemotherapy drugs can damage the body’s normal cells as well as the abnormal cancer cells. However, targeted therapy drugs recognize specific molecules found on cancer cells and leave most of the body’s normal cells alone.

People with stage 3 or stage 4 epithelial ovarian cancer may take the targeted therapy drug bevacizumab (Avastin) along with chemotherapy.

Targeted therapy drugs may also be a good fit when a person’s epithelial ovarian cancer contains gene changes that make it harder for cells to fix damage. Cancer cells with such mutations may be more sensitive to a group of drugs called poly (ADP-ribose) polymerase (PARP) inhibitors. These inhibitors target a protein in cells that repairs damage (PARP). PARP inhibitors target cancer cells, making it impossible for them to self-repair, leading to their being killed off. Drugs in the PARP inhibitor family include olaparib (Lynparza), rucaparib (Rubraca), and niraparib (Zejula).

Clinical Trials

Researchers test new treatment options during clinical trials. People who participate in clinical trials may be able to access new therapies that are not yet part of standard treatment plans. Clinical trials may be available for people with different stages of ovarian cancer. Some people use clinical trials as their first treatment option, while others may choose to enroll after trying other therapies.

What Is the Outlook for Epithelial Ovarian Cancer?

Epithelial ovarian cancer is often diagnosed at a more advanced stage, after it has begun to spread to nearby or more distant tissues. The cancer’s stage at diagnosis plays a big role in survival rates:

• When epithelial tumors are located in only someone’s ovaries, they are 93 percent as likely to live five years or more, compared to people without ovarian cancer.
• If epithelial tumors have grown into a person’s nearby tissues, they are 75 percent as likely to live five years or more after being diagnosed.
• When epithelial cancer has spread to other parts of someone’s body, they are 31 percent as likely to live for at least five years.

In order to determine an individual’s outlook, doctors use prognostic factors — characteristics that increase a person’s chances of having a good or poor outcome. One of the strongest prognostic factors for epithelial tumors is residual disease. This is a measure of how much cancer is left in the body after surgery. People with little or no residual disease are more likely to have a good outlook. That is why being treated by a doctor experienced in ovarian cancer can be especially beneficial.

Other prognostic factors that increase the chance someone will have a poor outlook include:

• Older age (more than 65 years old)
• Poor overall health
• Obesity
• Presence of ascites (fluid buildup in the abdomen)
• High tumor grade (indicates more abnormal-looking and faster-growing cells)
• Subtype of ovarian cancer (high-grade serous carcinoma, mucinous carcinoma, or clear cell carcinoma)

If you would like to know more about your individual prognosis, talk to your health care team. Your doctor is familiar with your personal characteristics and can help you understand how they influence your outlook.

Talk With Others Who Understand

On MyOvarianCancerTeam, the social network for people with ovarian cancer and their loved ones, more than 4,000 members come together to ask questions, give advice, and share their stories with others who understand life with the condition.

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