Ovarian epithelial cancer is the most common form of ovarian cancer, accounting for about 90% of all cases. This type develops in the thin tissue covering the ovaries, fallopian tubes, or peritoneum. Because symptoms often appear late in the disease, many people are diagnosed after the cancer has already spread, making early detection and awareness of warning signs crucial.
Understanding Epithelial Ovarian Cancer
Epithelial ovarian cancer develops in the epithelial tissue, which is a thin layer of cells that covers the outer surface of the ovaries. This same type of tissue lines the fallopian tubes and the peritoneum, the membrane that covers organs in the abdomen. Because these cancers form in similar tissues and behave in comparable ways, medical professionals typically group fallopian tube cancer and primary peritoneal cancer together with epithelial ovarian cancer when discussing treatment and outcomes.[1]
Scientists believe that many ovarian cancers actually begin in the cells at the very end of the fallopian tubes, called the fimbriae, before spreading to the ovaries. This discovery has changed how doctors understand where these cancers originate. The cancer cells can then spread into the abdominal cavity, where they may attach to other organs such as the intestines, bladder, or uterus.[3]
One of the most challenging aspects of epithelial ovarian cancer is that it rarely causes noticeable symptoms in its earliest stages. By the time most people begin experiencing discomfort or other warning signs, the disease has often already progressed. This is why understanding your risk factors and maintaining regular check-ups with your gynecologist is so important.[1]
Types of Epithelial Ovarian Cancer
Not all epithelial ovarian cancers are the same. Doctors classify these cancers into different subtypes based on how the cells look under a microscope and how they behave. Understanding which type you have matters because different subtypes can respond differently to treatment.[4]
High-grade serous carcinoma, often abbreviated as HGSOC, is by far the most common and aggressive subtype. It accounts for about three out of every four epithelial ovarian cancers. Experts believe this type grows slowly at first in the fallopian tubes, but once it reaches the ovaries, it spreads rapidly. Nearly 70% of cases are stage 3 or 4 by the time they’re discovered, meaning the cancer has already spread to nearby organs and lymph nodes.[1]
Endometrioid carcinoma is the second most common type. This cancer is more frequently seen in people who have endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus. The good news is that endometrioid carcinoma often responds better to chemotherapy than some other types, and most cases are diagnosed at an early stage when they’re still low grade.[4]
Clear cell carcinoma can also be linked to endometriosis. People of Asian descent face higher risk for this type. Unfortunately, clear cell carcinoma tends to be more advanced at diagnosis and doesn’t respond as well to standard chemotherapy treatments.[1]
Low-grade serous ovarian carcinoma, or LGSOC, represents about one in ten epithelial ovarian cancers. This type typically affects younger people, often in their mid-forties. These cancers grow slowly but persistently over a long period. They tend not to respond well to chemotherapy, which means surgery often becomes the primary treatment option.[1]
Mucinous carcinoma tumors are distinctive and tend to grow quite large, sometimes reaching around 8 inches or 20 centimeters. However, they typically stay confined to the ovaries and respond well to treatment. Primary squamous cell carcinoma of the ovary often develops from non-cancerous conditions like ovarian cysts, endometriosis, or growths called Brenner tumors. When caught early, it also responds well to treatment.[1]
How Common Is Epithelial Ovarian Cancer
Epithelial ovarian cancer is one of the most serious gynecological cancers women face. It ranks as the leading cause of death among women diagnosed with cancers of the reproductive system and the second most common gynecologic malignancy in the United States. Worldwide, it ranks as the third most common gynecologic cancer.[2]
In the United States, approximately 20,000 women are diagnosed with ovarian cancer each year. More than half of all diagnoses occur in women over age 65 who have gone through menopause. The disease causes about 13,000 deaths annually in the United States. Globally, ovarian cancer is diagnosed in an estimated 300,000 people each year and causes roughly 180,000 deaths.[3][16]
The high death rate from ovarian cancer stems largely from late diagnosis. Only about 20% of cases are caught before the cancer has spread beyond the ovaries. When the disease is confined to the ovary and detected early, the survival rate can be as high as 93% with aggressive treatment. However, because symptoms often don’t appear until the cancer has advanced, overall five-year survival rates hover around 50%.[7][16]
Symptoms and Warning Signs
One of the most troubling aspects of epithelial ovarian cancer is that it rarely produces symptoms when it’s most treatable. As the disease progresses and spreads into the peritoneum, fluid begins accumulating in the abdomen. This fluid buildup causes many of the symptoms people eventually notice.[1]
Common symptoms include abdominal pain, bloating, and a feeling of pressure or swelling in the belly or pelvic area. Many people find they have difficulty eating or feel full very quickly after starting a meal. Nausea and vomiting can occur. These symptoms might seem minor or be mistaken for digestive problems, which is part of why the cancer often goes undetected for so long.[1][5]
Less common symptoms include changes in bowel habits, such as new constipation or diarrhea. Some people experience a strong urge to urinate or find themselves urinating more frequently than usual. Vaginal bleeding or discharge might occur, as well as fatigue and back pain. These symptoms are considered less common but should still prompt a conversation with your doctor.[1][6]
What Causes Epithelial Ovarian Cancer
The exact cause of epithelial ovarian cancer remains unknown. Scientists believe that cancer starts when something goes wrong in a cell’s DNA, causing changes called mutations. These mutations can make cells grow uncontrollably or prevent them from repairing damage properly. Over time, these abnormal cells accumulate and form tumors.[1]
Experts think many ovarian cancers actually originate in cells at the fimbriated ends of the fallopian tubes. These early cancer cells then spread to the ovary where they continue to grow. Sometimes cancer begins in the peritoneum and spreads to the ovaries rather than the other way around. This is why fallopian tube cancer and primary peritoneal cancer are treated the same way as ovarian cancer.[3]
Some gene mutations are inherited, meaning they’re passed down through families. Everyone carries these mutations in all their cells from birth. The most commonly mutated genes that lead to ovarian cancer are BRCA1 and BRCA2. About 10% to 15% of epithelial ovarian tumors involve BRCA mutations. These same gene changes can also increase breast cancer risk. Overall, up to one in five people with ovarian cancer have inherited gene mutations.[8]
More often, ovarian cancer develops from acquired gene changes that occur during a person’s lifetime rather than being inherited. Various environmental and lifestyle factors can contribute to these acquired mutations, though researchers don’t fully understand all the mechanisms involved.[20]
Risk Factors
Several factors can increase a person’s chances of developing epithelial ovarian cancer. Age is one of the most important risk factors. More than half of all ovarian cancer diagnoses occur in people over 65 who have gone through menopause. The chance of getting cancer increases as you get older.[1][8]
Family history plays a significant role in ovarian cancer risk. Having a mother, sister, or daughter with ovarian cancer increases your risk considerably. If you have a first-degree relative with ovarian cancer, your chances of developing the disease rise. This family connection often indicates inherited gene mutations that can be passed down through generations.[3]
Inherited gene mutations, particularly changes in the BRCA1 or BRCA2 genes, substantially increase risk. Women with the BRCA1 mutation face a 39% to 40% lifetime risk of developing ovarian cancer, while those with BRCA2 mutations have about a 17% risk. For comparison, women without these mutations have about a one in seventy-eight lifetime risk. Other hereditary conditions, such as hereditary nonpolyposis colorectal cancer (also called Lynch syndrome), also increase ovarian cancer risk.[7][8]
Having had breast cancer or colon cancer previously increases the likelihood of developing epithelial ovarian cancer. Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, is associated with higher risk, particularly for endometrioid and clear cell subtypes.[8]
Using hormone therapy after menopause increases risk, as does obesity, defined as having a body mass index greater than 30. Interestingly, tall height has also been identified as a risk factor, though the reasons for this association aren’t fully clear.[8][20]
Prevention Strategies
While you cannot completely prevent epithelial ovarian cancer, certain strategies may help reduce your risk. For women at very high risk due to inherited gene mutations, particularly BRCA1 or BRCA2 changes, preventive surgery might be considered. This involves removing the ovaries and fallopian tubes before cancer develops. Doctors may recommend this option for women who have completed their families and carry high-risk genetic mutations.[3]
Using birth control pills has been associated with reduced ovarian cancer risk. However, this decision involves weighing potential benefits against other health considerations and should be discussed thoroughly with your healthcare provider.[20]
For women with a strong family history of ovarian or breast cancer, genetic counseling and testing can provide valuable information. Knowing whether you carry high-risk gene mutations allows you to make informed decisions about screening and prevention strategies. Doctors often recommend genetic testing for people diagnosed with ovarian cancer to look for inherited mutations.[8]
Maintaining a healthy lifestyle may contribute to lower cancer risk overall, though more research is needed specifically for ovarian cancer. Not smoking, maintaining a healthy weight, and staying physically active are beneficial for general health and may help with cancer prevention. For women already diagnosed with ovarian cancer, quitting smoking and remaining physically active have been associated with better survival outcomes.[23]
How Ovarian Cancer Changes the Body
Understanding what happens in your body when cancer develops can help you make sense of your symptoms and treatment. Epithelial ovarian cancer begins when cells in the epithelial tissue start growing abnormally. These cells can be distinguished under a microscope and are classified as serous, mucinous, endometrioid, or clear cell types. The way these cells look helps doctors understand how aggressive the cancer might be.[7]
As the cancer grows, it often spreads into the abdominal cavity. Cancer cells can implant themselves on other organs, including the uterus, intestines, bladder, and the omentum, which is a fatty tissue that covers abdominal contents. Sometimes cancer cells spread to the lungs. On rarer occasions, they enter the bloodstream or lymphatic system, which is the network of vessels and nodes that helps fight infection, and travel to many other parts of the body.[7]
A hallmark characteristic of epithelial ovarian, fallopian tube, and peritoneal cancers is their tendency to spread early throughout the peritoneal cavity. This widespread dissemination is why many people are diagnosed at advanced stages. The cancer cells floating in the peritoneal fluid can settle on any surface within the abdomen, creating multiple areas of disease.[15]
When cancer spreads into the peritoneum, fluid often accumulates in the abdomen, a condition called ascites. This fluid buildup causes the bloating and abdominal swelling that many people with advanced ovarian cancer experience. The accumulation of fluid and the presence of tumors pressing on other organs account for many of the symptoms people feel.[1]
Cancer cells are graded from 1 to 3 based on how abnormal they look under a microscope. Grade 1 cells look relatively similar to normal tissue and tend to grow more slowly. Grade 3 cells look very different from normal tissue and typically grow and spread more rapidly, leading to a more serious prognosis.[7]
