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This page was reviewed under our medical and editorial policy by

Ruchi Garg, MD, CTCA Enterprise Chair, Gynecologic Oncology.

This page was reviewed on January 16, 2023.

Epithelial ovarian cancer

Ovarian cancer forms when abnormal cells grow in an ovary to form a tumor. If the growth isn’t caught early, the cancer cells may spread to nearby tissues and other areas of the body. Most ovarian cancers are epithelial ovarian cancers.

Epithelial ovarian cancers originate from the tissue covering the ovary. Epithelial ovarian, fallopian tube and primary peritoneal carcinoma are often grouped together because they share similar characteristics and have the same embryological cell origin, so they're treated the same way.

The U.S. Centers for Disease Control and Prevention (CDC) reports that in the United States, ovarian cancer is the second-most common gynecological cancer, and it causes more deaths than any other female reproductive cancer. According to the American Cancer Society (ACS), about 85 to 90 percent of malignant ovarian cancers are ovarian epithelial carcinoma. Germ cell and stromal cell ovarian cancers are rarer but more common in younger women.

This overview will cover the basic facts about epithelial ovarian cancer, including:

What are epithelial ovarian tumors?

Epithelial cells are found on the outer surface of the ovaries. Tumors in these cells are classified as benign, borderline or malignant.

Benign tumors are non-cancerous and will not spread or lead to serious health problems. Borderline tumors don't appear cancerous, but they’re slow-growing and may become harmful if allowed to grow.

Malignant epithelial tumors are called carcinomas. They’re invasive cancers, grow more rapidly and may spread to other areas of the body.

Types of epithelial ovarian cancer

In general, epithelial ovarian carcinomas are categorized into four different cell typles:

  • Serous carcinoma
  • Mucinous carcinoma
  • Endometrioid carcinoma
  • Clear cell carcinoma

According to the ACS, serous carcinomas are the most common, accounting for 52 percent of epithelial ovarian carcinomas.

Serous carcinoma

Serous epithelial ovarian cancer tumors are low-grade or high-grade. Low-grade tumors are slower in developing than high-grade ones.

High-grade serous ovarian carcinoma is the most common invasive epithelial ovarian cancer type. It's treated the same way as fallopian tube cancer and primary peritoneal carcinoma, and it’s often diagnosed at advanced stages.

Mucinous carcinoma

Mucinous epithelial ovarian cancer is a rare subtype of epithelial ovarian cancer. The ACS estimates that 6 percent of epithelial ovarian cancers are mucinous. This type of epithelial ovarian cancer has cells that grow large, are filled with fluid and have a foamy appearance. These tumors are mainly made of mucus-coated cancer cells.

Endometrioid carcinoma

According to the ACS, endometrioid carcinomas account for 10 percent of epithelial ovarian cancers. They’re sometimes linked to endometriosis—a condition of the uterus’ lining (endometrium), where endometrial cells grow outside the uterus.

Clear cell carcinoma

According to the ACS, clear cell carcinomas account for 6 percent of epithelial ovarian cancers. Clear cell ovarian cancer is more often diagnosed in younger females and found in early stages.

Endometriosis is considered a risk factor for clear cell carcinoma. Clear cell ovarian cancer is commonly linked to ARID1A mutations, which have been found in the endometrial tissue surrounding clear cell tumors.

Symptoms of epithelial ovarian cancer

Ovarian cancer may cause a variety of symptoms. Patients may experience symptoms in the early stages, but they may not be noticeable until the cancer has progressed to more advanced stages.

Symptoms of epithelial ovarian cancer include:

  • A feeling of fullness, quickly after eating
  • Loss of appetite
  • Bloating
  • Abdominal pain
  • Pelvic pain
  • Ascites (fluid in the abdomen) if cancer spreads to the peritoneum
  • Urinary symptoms, including urgency and frequency
  • Vaginal bleeding
  • Gastrointestinal challenges, including upset stomach, nausea, constipation and diarrhea

People who experience any of the above symptoms for more than a few weeks or notice changes in their ovarian health should immediately reach out to their doctor.

Causes and risk factors

Cancer is often the result of gene mutations that cause uncontrolled cell growth and prevent healing. Unchecked cell growth then often leads to tumor development.

Some gene mutations are inherited. Common gene mutations linked to ovarian cancer are BRCA1 and BRCA2. About 20 percent to 25 percent of ovarian cancers result from inherited BRCA1 and BRCA2 gene mutations. Additional gene mutations are linked to ovarian cancer, but those are rarer.

Having BRCA1 and BRCA2 mutations may also increase the risk of breast cancer. Women with a personal history of breast cancer or a family history of breast cancer may have an increased risk for ovarian cancer.

Different environmental and lifestyle factors linked to gene mutations might also increase the risk for epithelial ovarian cancer.

Risk factors for ovarian cancer include:

Age: Ovarian cancer in people younger than 40 is rare, and at least half of ovarian cancers occur after age 63, according to the ACS.

Family history: People with a family history of ovarian cancer, breast cancer or colorectal cancer may have a higher risk. The risk may be even higher for people with a first-degree relative with ovarian cancer.

Patients should discuss risk factors for ovarian cancer with their doctors. A health care provider may recommend ways to reduce risk and give advice on screening options.

Epithelial ovarian cancer diagnosis

No one test may detect epithelial ovarian cancer early. The doctor may start the diagnostic process if symptoms of ovarian cancer are reported. A health care provider may notice signs of cancer (such as a growth or enlarged organ) when performing an exam of the vagina, cervix and other pelvic tissues.

A CA-125 blood test may detect signs of cancer. The health care provider may request the test if a patient has risk factors or experiences symptoms that suggest ovarian cancer. However, high CA-125 levels alone aren't a reliable indicator of ovarian cancer and may be linked to non-cancerous conditions such as endometriosis and uterine fibroids. However, high levels of CA-125 often prompt further testing.

Imaging may be requested to examine the reproductive organs. Imaging tests may include transvaginal ultrasound, computed tomography or magnetic resonance imaging.

Laparoscopy is a surgical procedure that may be used as a diagnostic test to allow a clinician to examine the reproductive organs, while also enabling the provider to take tumor tissue samples for biopsy.

A biopsy is the only way to determine whether a mass is cancerous or benign. Once the sample is taken, it’s examined under a microscope to determine the presence and type of ovarian cancer. A mass on an ovary or fallopian tube may be biopsied during surgery.

If ascites formed in the abdomen, samples of the fluid are taken to aid in a diagnosis as part of a procedure called paracentesis, which involves injecting a needle into the abdomen to remove fluid from the abdominal cavity. The fluid is sent to a lab for analysis.

Staging

If the patient is diagnosed with epithelial ovarian cancer, the doctor will want to know how advanced it is. The same testing performed to diagnose ovarian cancer helps determine staging.

There are four stages of ovarian cancer. Higher stages mean more advanced cancer that has spread from the original site to neighboring organs, tissues and lymph nodes.

Stage 1: The cancer is in one or both ovaries or one or both fallopian tubes. In this stage, the cancer hasn’t spread past its initial location.

Stage 2: The cancer has spread beyond the ovaries and fallopian tubes to neighboring tissues in the pelvis.

Stage 3: The cancer has spread to abdominal structures, like the lining (peritoneum).

Stage 4: The cancer has metastasized to distant body parts, such as the lungs, spleen or liver.

Treatment

Prognosis and treatment options for epithelial ovarian cancer depend on factors such as the type of cancer, the stage and the grade. The cancer stage tells the care team how big the cancer is and whether it’s spread, while the grade refers to how abnormal the cells look under a microscope.

Other factors include whether the cancer has spread to the peritoneum, the patient's age, the patient’s general health and whether it’s a new or recurring cancer.

Treatment options for epithelial ovarian cancer include:

Surgery

Surgery removes as much of the cancer as possible in the affected ovaries and connective reproductive organs. Surgery may be performed at any stage unless it wouldn’t be helpful because of the patient’s age, health or other concerns. 

Chemotherapy

The vast majority of epithelial ovarian cancer patients undergo chemotherapy at some point in their treatment journey.

Targeted therapy

These medicines attack proteins in cells without harming healthy cells. They’re sometimes used with other treatments, including surgery and chemotherapy. Low-grade serous ovarian cancer tends to be resistant to chemotherapy, which has led to a focus on targeted therapy.

Hormone therapy

Hormone therapy is rarely used to treat epithelial ovarian cancer, but it is used for ovarian stromal tumors. Hormone therapies that might be used to treat ovarian cancer include tamoxifen and anastrozole.

Palliative care

Palliative care may help ovarian cancer patients manage other aspects of epithelial ovarian cancer during treatment, including emotional stress, medication side effects, pain and symptoms that affect quality of life.

Epithelial ovarian cancer survival rates

Epithelial ovarian cancer prognosis depends on various factors, including age and overall health.

Early detection generally means a better prognosis. For ovarian cancer diagnosed and treated at stage 1, the five-year relative survival rate is about 94 percent, according to the ACS. About 20 percent of ovarian cancers are diagnosed at stage 1.

According to the National Cancer Institute, the overall five-year relative survival rate for ovarian cancers is 49.7 percent across all stages. The type of ovarian cancer also affects the survival rate. According to the ACS, the five-year relative survival rate for invasive epithelial ovarian cancer is about 49 percent.

Survival rates for ovarian cancer are estimates and are based on a percentage of people with the same cancer type and stage who are still alive five years after they were diagnosed. These percentages can’t tell patients how long they’ll live or how strong their prognosis is, but they offer an understanding of potential outcomes. A patient's cancer care team may provide additional information about their treatment options and outlook.

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