What Is Ovarian Cancer?
A plain-language overview of ovarian, fallopian tube, and primary peritoneal cancer, where it starts, and how it is found, based on National Cancer Institute resources.
Source: National Cancer Institute · Verified 2026-07-02
The 30-second version
Ovarian epithelial cancer, fallopian tube cancer, and primary peritoneal cancer form in the same kind of tissue and are treated the same way. The ovaries are a pair of organs in the female reproductive system that make eggs and hormones. These cancers often cause no early symptoms and are frequently advanced when found.
Key takeaways
- Ovarian epithelial cancer, fallopian tube cancer, and primary peritoneal cancer form in the same kind of tissue and are treated the same way.
- The ovaries are a pair of almond-sized organs in the pelvis, one on each side of the uterus, that make eggs and female hormones.
- These cancers may cause no early signs, so they are often advanced when found.
- A family history of ovarian cancer raises the risk, and about 20% of ovarian cancers are hereditary.
- Some ovarian cancers are linked to inherited changes in the BRCA1 or BRCA2 genes.
- Signs and symptoms can include pain or swelling in the abdomen and feeling full quickly.
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The full explanation.
The simple version
Ovarian epithelial cancer, fallopian tube cancer, and primary peritoneal cancer are diseases in which cancer cells form in the tissue covering the ovary or lining the fallopian tube or peritoneum. These three cancers form in the same kind of tissue and are treated the same way.
Ovarian epithelial cancer is the most common cancer that affects the ovary. Less common types of ovarian tumors include ovarian germ cell tumors and ovarian low malignant potential (borderline) tumors.
In short: ovarian, fallopian tube, and primary peritoneal cancers form in the same kind of tissue and are treated the same way.
Where these cancers start
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 long, slender tubes, one on each side of the uterus. Eggs pass from the ovaries, through the fallopian tubes, to the uterus. Cancer sometimes begins at the end of the fallopian tube near the ovary and spreads to the ovary.
The peritoneum is the tissue that lines the abdominal wall and covers organs in the abdomen. Primary peritoneal cancer is cancer that forms in the peritoneum and has not spread there from another part of the body. Cancer sometimes begins in the peritoneum and spreads to the ovary.
Risk factors
A family history of ovarian cancer in a first-degree relative (mother, daughter, or sister) raises the risk of ovarian cancer. Other risk factors can include inherited changes in the BRCA1 or BRCA2 genes, other hereditary conditions such as Lynch syndrome, endometriosis, postmenopausal hormone therapy, and obesity. Older age is the main risk factor for most cancers.
Hereditary ovarian cancer makes up about 20% of all cases of ovarian cancer. Because some cases run in families, genetic tests are sometimes done for members of families with a high risk of cancer.
In short: family history and certain inherited gene changes can raise the risk of ovarian cancer.
Signs and finding it
Ovarian epithelial, fallopian tube, or peritoneal cancer may not cause early signs or symptoms. When signs or symptoms do appear, the cancer is often advanced. Signs and symptoms may include:
- Pain, swelling, or a feeling of pressure in the abdomen or pelvis.
- A sudden or frequent urge to urinate.
- Trouble eating or feeling full.
- A lump in the pelvic area.
- Stomach problems, such as gas, bloating, or constipation.
These signs and symptoms can also be caused by other conditions. If they get worse or do not go away on their own, check with your doctor so any problem can be found and treated as early as possible.
Everyone's situation is different. Your care team is the best source of information about your own health and any next steps.
Watch instead
Animated lessons are in production. Here’s the planned video slate for this topic — each one will be based on the same NCI-sourced explanation you’re reading.
What Is Ovarian Cancer: the quick overview
A one-breath explanation you can watch before an appointment.
Coming soonWhat Is Ovarian Cancer, explained simply
The core ideas with friendly animation and plain language.
Coming soonUnderstanding what is ovarian cancer — full lesson
A deeper walkthrough covering the key takeaways and common questions.
Coming soonVideo transcript▾
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Suggested animation storyboard▾
- 1Open on a calm title card: "What Is Ovarian Cancer?" with the Cancer Explained mark.
- 2Narrator reads the 30-second summary while a soft animated diagram builds on screen: "Ovarian epithelial cancer, fallopian tube cancer, and primary peritoneal cancer form in the same kind of tissue and are treated the same way. The ovaries are a pair of organs in the female reproductive system that make eggs and hormones. These cancers often cause no early symptoms and are frequently advanced when found."
- 3Scene 2: illustrate the idea — "Ovarian epithelial cancer, fallopian tube cancer, and primary peritoneal cancer form in the same kind of tissue and are treated the same way."
- 4Scene 3: illustrate the idea — "The ovaries are a pair of almond-sized organs in the pelvis, one on each side of the uterus, that make eggs and female hormones."
- 5Scene 4: illustrate the idea — "These cancers may cause no early signs, so they are often advanced when found."
- 6Close on a reminder card: this is educational only; talk with your healthcare team, and a link to the NCI source.
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Quick knowledge check
According to this article, what do the ovaries do?
Frequently asked questions
▸Where does ovarian cancer start?
The ovaries are a pair of organs in the female reproductive system, in the pelvis, one on each side of the uterus. Ovarian epithelial cancer forms in the tissue covering the ovary. Closely related cancers form in the lining of the fallopian tube or the peritoneum, the tissue that lines the abdomen. These cancers form in the same kind of tissue and are treated the same way.
▸What do the ovaries do?
Each ovary is about the size and shape of an almond. The ovaries make eggs and female hormones. Eggs pass from the ovaries, through the fallopian tubes, to the uterus.
▸Why is ovarian cancer often found late?
Ovarian epithelial, fallopian tube, or peritoneal cancer may not cause early signs or symptoms. When signs or symptoms do appear, the cancer is often advanced. These signs may include pain, swelling, or pressure in the abdomen or pelvis, feeling full quickly, and needing to urinate often.
▸Does family history affect ovarian cancer risk?
Yes. Women who have a family history of ovarian cancer in a first-degree relative (mother, daughter, or sister) are at increased risk. Hereditary ovarian cancer makes up about 20% of all cases. Some cases are linked to inherited changes in the BRCA1 or BRCA2 genes.
▸Are ovarian, fallopian tube, and peritoneal cancers the same?
Ovarian epithelial cancer, fallopian tube cancer, and primary peritoneal cancer form in the same type of tissue and are treated the same way. Cancer sometimes begins near the end of a fallopian tube and spreads to the ovary, or begins in the peritoneum and spreads to the ovary.
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Questions to ask your healthcare team
Consider bringing these questions to your next appointment.
- What type of ovarian cancer do I have?
- Should I consider genetic testing for BRCA1 or BRCA2 changes?
- What tests do I need to learn more about my cancer?
- What are my treatment options, and what are the possible side effects?
- How will treatment affect my daily life?
- Where can I find reliable information and support?
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