What Is Peritoneal Cancer?

Written by Lisa Guthrie, Annie Stuart
Medically Reviewed by Raja Durai Sam Nishanth, MBBS, MD on February 16, 2026
6 min read

Peritoneal cancer is a rare cancer that forms in the thin layer of tissue that lines the abdomen. It also covers the uterus, bladder, and rectum. This layer is called the peritoneum and is made of epithelial cells. It produces a fluid that helps organs move smoothly inside the abdomen.

Peritoneal cancer is not the same as intestinal or stomach cancer. And it shouldn't be confused with cancers that spread (metastasize) to the peritoneum. Peritoneal cancer startsin the peritoneum. So, it's called primary peritoneal cancer.

Peritoneal cancer acts and looks like ovarian cancer. This is mainly because the surface of the ovaries, just like the peritoneum, is made of epithelial cells. So, peritoneal cancer and a type of ovarian cancer cause similar symptoms. Doctors treat them in much the same way.

You can have peritoneal cancer even if your ovaries have been removed. Peritoneal cancer can happen anywhere in the abdominal space. It affects the surface of organs inside the peritoneum.

The exact cause of peritoneal cancer is not known. But there are different ideas about how it begins. Some believe it comes from ovarian tissue cells that remain in the abdomen after a fetus grows. Others think the peritoneum itself goes through changes that make it more like the ovaries.

Primary peritoneal cancer is more common in women than in men. Women at risk for ovarian cancer are also at increased risk for peritoneal cancer. This risk is even higher in those who have the BRCA1 and BRCA2 genetic mutations (changes). Older age is another risk factor for peritoneal cancer.

Just as with ovarian cancer, peritoneal cancer can be hard to findin the early stages. That's because its symptoms are hard to pinpoint. When clear symptoms do happen, the disease has often advanced. Then, symptoms are often like those of ovarian cancer. Many of these symptoms are due to the buildup of fluid (ascites) in the abdomen. Peritoneal cancer symptoms may include:

 

In addition to asking about symptoms, your doctor will look at your medical history and do a physical exam, which involves checking for abnormalities in these areas:

Tests you may have include:

Ultrasound. This uses high-frequency sound waves to produce a picture called a sonogram.

CA-125 blood test. This test measures levels of a chemical in the blood called CA-125. If levels are high, peritoneal or ovarian cancer may be present. But CA-125 can be high for other reasons as well. So, this test cannot confirm a diagnosis of these cancers.

CT scan. A computer linked to an X-ray machine makes detailed pictures of the inside of the body.

Lower gastrointestinal (GI) series or barium enema. In this test, you first get an enema with a white, chalky solution called barium. This outlines the colon and rectum on an X-ray. This allows doctors to spot some tumors and other problems.

Upper GI series. During this test, barium is swallowed, and the esophagus, stomach, and duodenum (the first part of the small intestine) are outlined on an X-ray.

Biopsy. A surgeon removes tissue by opening the abdomen either during a laparotomy or by inserting tools through small holes in the abdomen (laparoscopy). If the doctor suspects cancer, they may remove one or more organs. A pathologist studies the tissue sample under a microscope to confirm a cancer diagnosis.

Paracentesis. In cases where surgery is not possible or another condition could be causing the fluid buildup, the doctor may instead remove fluid and look at it under a microscope. This is called paracentesis.

Ovarian and peritoneal cancers look the same under a microscope. So the pattern and location of any tumors help indicate which type of cancer is present.

You may have more than one type of treatment for peritoneal cancer. The type of treatment you have can depend on:

  • The stage and grade of the cancer
  • The size and location of the cancer
  • Your age and overall health

Treatments for peritoneal cancer include:

Surgery. Surgery not only helps with diagnosis but also may remove tumors. To stage and treat this cancer, a surgeon removes all visible disease. The surgeon may also remove the ovaries, fallopian tubes, and uterus. Depending upon what is found, the surgeon may also remove other tissue and organs. It is very important to have a gynecologic oncologist do this surgery. These specialists are familiar with gynecologic cancers and have greater success rates.

Chemotherapy. The drugs for treating peritoneal cancer are similar to those used for ovarian cancer. You may get these drugs by injection on an outpatient basis every one, two, or three weeks. Sometimes, chemotherapy is delivered directly into the abdomen through a catheter that was placed under the skin during surgery. This is called intraperitoneal chemotherapy. You also get it about every three weeks, but it is a more complex treatment cycle.

Hyperthermic intraperitoneal chemotherapy (HIPEC). This involves delivering heated chemotherapy into the peritoneum after surgery. This technique is common for peritoneal cancer that has spread from the appendix, colon, or stomach.

Palliative care. Doctors often diagnose peritoneal cancer in advanced stages. Supportive care can help relieve symptoms of peritoneal cancer, such as pain, weight loss, or fluid buildup.

More therapies may be used, including targeted therapy, hormonal therapy, and radiation therapy for some advanced primary peritoneal cancers.

Primary peritoneal cancer prognosis (outlook) is best if all cancer is removed and a gynecologic surgeon and oncologist treat you. These doctors have special knowledge of gynecologic cancers.

Your doctors will closely watch you after treatment. Peritoneal cancer can spread quickly because the peritoneum has a lot of lymph and blood that can carry cancer cells to other parts. It's common for peritoneal cancer to come back after treatment. That's because it is often diagnosed in an advanced stage. You may need more than one round of chemotherapy or other surgeries.

Be sure to reach out for support as you go through treatment and healing.

Can peritoneal cancer be cured?

There's no cure for peritoneal cancer, but surgery and treatments can help you live longer if you have it. Palliative care can help ease pain and other symptoms.

Peritoneal cancer is a rare cancer that forms in the very thin membrane that lines the abdominal area. It's not easy to diagnose and is often found in later stages — after patients have had it for a while and it has spread. Treatments can help people with peritoneal cancer live longer, but it is very common for this cancer to come back.

What are the first signs of peritoneal cancer?

Some symptoms of peritoneal cancer aren't noticeable until the cancer spreads to nearby organs, such as the bladder, stomach, or intestines. Symptoms may include: 

  • Swelling or bloating in the belly
  • Losing weight without trying
  • Nausea and vomiting
  • No appetite
  • Feeling very tired

Is peritoneal cancer considered terminal?

Peritoneal cancer can be treated, but not cured. About 45% of people who get treatment (surgery and chemotherapy) that removes the tumor are alive five years later. If the cancer can't be completely removed, the five-year survival rate is 10%.