What is primary peritoneal cancer?

The peritoneum is a layer of tissue in the tummy (abdomen). The inner layer covers the surface of all the organs in the abdomen, such as the stomach, liver and bowel. The outer layer lines the wall of the abdomen.

When cancer starts in the peritoneum, this is called primary peritoneal cancer. We have separate information about:

Primary peritoneal cancer is rare. It can affect women, trans men and people assigned female at birth. It can also affect men, trans women and people assigned male at birth but this is very rare. It is diagnosed and treated in the same way as ovarian cancer.

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Types of primary peritoneal cancer

The most common cancer to start in the peritoneum is called epithelial cancer.

The different types of epithelial cancer are:

  • serous
  • mucinous
  • endometrioid
  • clear cell.

High-grade serous cancer is the most common type.

Borderline tumours

Borderline tumours are made up of abnormal epithelial cells, but they are not true cancers. They usually grow slowly and are unlikely to spread. They can sometimes behave more like a low-grade cancer, but this is rare.

Symptoms of primary peritoneal cancer

Primary peritoneal cancer often causes symptoms that are similar to other more common and less serious conditions. This can sometimes make it difficult to diagnose.

Symptoms can include:

  • a long-lasting bloated or swollen tummy
  • loss of appetite
  • feeling full quickly when you eat
  • pain in the lower tummy area or back
  • passing urine more often than usual
  • passing urine more urgently (feeling like you can't hold on).

If you have any of these symptoms for no reason, or you get these symptoms regularly (especially more than 12 times a month), your GP should offer you cancer tests.

Other symptoms may include:

  • a change in your normal bowel habit (diarrhoea or constipation)
  • weight gain or weight loss
  • unexplained or extreme tiredness (fatigue)
  • vaginal bleeding after your menopause.

If you are 50 years or older and develop symptoms of irritable bowel syndrome (IBS) for the first time, you should also have tests. IBS can cause bloating and changes in bowel habit, but it does not usually start after the age of 50.

Causes of primary peritoneal cancer

We do not know what causes cancer to start in the peritoneum. And because this cancer is rare, we know little about the risk factors that may increase the chances of it developing. The risk factors are likely to be similar to the risk factors for ovarian cancer.

Diagnosis of primary peritoneal cancer

You usually start by seeing your GP. The GP will ask about your symptoms and do an internal (vaginal) examination to check for any lumps or swelling.

They may also arrange for you to have:

  • a CA125 blood test
    This blood test checks for raised levels of a protein called CA125.
  • an ultrasound scan
    You may have ultrasound scans to check the organs inside the abdomen (tummy area) and the pelvis.

If your GP is worried about cancer, they will arrange for you to see a specialist doctor within 2 weeks. This specialist is usually a gynaecologist (a doctor who treats female reproductive system problems).

Some people are admitted directly to hospital if they have a symptom that is making them very unwell.

At the hospital

The specialist doctor will ask you about your general health, any previous health problems, and whether you have any history of cancer in your family. They will do an internal (vaginal) examination again. If you have not already had a CA125 blood test and ultrasound, they will usually arrange for you to have these tests.

The doctor may use the results of your tests to check your Risk of Malignancy Index (RMI) score. This is a system that checks how likely it is that your symptoms are caused by cancer. It takes into account:

  • whether you have gone through the menopause
  • the level of CA125 in your blood
  • the results of your ultrasound.

Further tests

The specialist doctor may also organise further tests. These may help your team diagnose the cancer and also help them plan your treatment. You may have:

  • CT scan
    A CT scan takes a series of x-rays, which build up a 3D picture of the inside of the body.
  • fluid taken from the abdomen
    Sometimes swelling or bloating in the tummy is caused by a build-up of fluid. This is called ascites. If you have ascites, your doctor may want to take a sample of this fluid to check for cancer cells.
    The doctor injects some local anaesthetic into the skin on your tummy (abdomen) to make it numb. They gently pass a small needle through the skin and collect some fluid in a syringe. The fluid is sent to the laboratory to be examined.
  • biopsy
    This is when the doctor removes a small sample (biopsy) from the lump or abnormal area. The sample is then sent to the laboratory and looked at under a microscope.
  • genetic testing
    Your doctor may talk with you about having a blood test to look for genetic changes that are linked to cancer. This is only done if you have certain types of cancer, such as high-grade serous or endometrioid cancer.

Waiting for test results can be a difficult time. We have more information that may help.

Staging and grading of primary peritoneal cancer

The stage of a cancer describes the size and position of the cancer and whether it has spread. Grading describes how the cancer cells look under the microscope compared with normal cells. Knowing the stage and grade helps your doctors plan the best treatment for you.

Your doctor will not usually know the exact stage of the cancer until it has been removed with surgery. If you have not had surgery, they can use the results of your tests to decide the stage of the cancer.

We have more information about staging and grading of primary peritoneal cancer.

Treatment for primary peritoneal cancer

A team of specialists will meet to discuss the best possible treatment for you. This is called a multidisciplinary team (MDT).

Your cancer doctor or specialist nurse will explain the different treatments and their side effects. They will also talk to you about the things you should consider when making treatment decisions.

Primary peritoneal cancer is treated in the same way as ovarian cancer. The main treatments are: 

  • Surgery
    Surgery is one of the main treatments. The aim is to remove all of the cancer.
  • Chemotherapy
    Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells. Carboplatin is the main chemotherapy drug used. It may be given in combination with paclitaxel.

Targeted therapies may be used to treat primary peritoneal cancer that has come back or advanced cancer. Targeted therapies interfere with the way cells grow.

Radiotherapy is sometimes used to treat an area of cancer that has come back when other treatments are no longer possible. It may also be used to control symptoms, such as bleeding, pain or discomfort. This is known as palliative radiotherapy.

Other treatments are also used to control symptoms caused by advanced cancer. This may include a procedure to drain fluid called ascites, that can build-up in the tummy.

After primary peritoneal cancer treatment

After your treatment, you will have regular check-ups. These are usually every few months to start with. If you have any problems or notice new symptoms between appointments, let your doctor know as soon as possible.

You may get anxious between appointments. This is natural. It may help to get support from family, friends or a support organisation.

Macmillan is also here to support you. If you would like to talk, you can:

CA125 blood tests

CA125 blood tests are sometimes done as part of your follow-up, but this is not always needed. A rising CA125 level may be a sign that the cancer has returned. But for most people, it is just as effective to wait for symptoms of cancer to develop and then start treatment again.

Starting treatment before you have symptoms:

  • is no more effective at controlling the cancer
  • means you will have side effects of treatment sooner.

Your cancer doctor or nurse can give you more information about this.


After treatment, it can take time to work out what feels normal for you. You may worry that every ache or pain you have is a sign of cancer returning.,

If you develop any new symptoms, do not wait for a follow-up appointment. Contact your specialist nurse or see your GP. They can arrange for you to be seen by your cancer doctor if needed.

Primary peritoneal cancer that comes back

Primary peritoneal cancer that comes back can usually be treated again with more chemotherapy, targeted therapies and sometimes more surgery. Some people will have several courses of chemotherapy or other treatments spaced over a few years. The aim of treatment is to control the cancer for as long as possible and to manage any symptoms.

Finding out you have advanced cancer can be difficult to cope with. You may feel shocked and find it hard to understand. Or you may have questions about what to expect. Your doctor and specialist nurse are there to help.

We have more information about coping with advanced cancer that you may find helpful.

Your sex life after treatment for primary peritoneal cancer

Cancer and cancer treatment can cause physical and emotional changes that may affect your sex life. For example, if you have not been through the menopause already, your cancer treatment may cause it.

Well-being and recovery

Even if you already have a healthy lifestyle, you may choose to make some positive lifestyle changes after treatment.

Making small changes such as eating well and keeping active can improve your health and wellbeing and help your body recover.

About our information

  • References

    Below is a sample of the sources used in our ovarian cancer information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk

    Fotopoulou C, et al. British Gynaecological Cancer Society (BGCS) epithelial ovarian/ fallopian tube/ primary peritoneal cancer guidelines: recommendations for practice. European Journal of Obstetrics, gynecology, and reproductive biology. 2017. 213: 123-139.

    National Institute for Health and Care Excellence. Ovarian cancer: recognition and initial management. Clinical guideline (CG122). April 2011. Available from: www.nice.org.uk/Guidance/CG122 (accessed June 2017). 

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Professor David Luesley, Professor of Gynaecological Oncology.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Content under review

Due to the pandemic, there have been delays in us updating this information as quickly as we would have wanted. Our team is working hard to put this right.

The language we use

We want everyone affected by cancer to feel our information is written for them.

We try to make sure our information is as clear as possible. We use plain English, avoid jargon, explain any medical words, use illustrations to explain text, and make sure important points are highlighted clearly.

We use gender-inclusive language and talk to our readers as ‘you’ so that everyone feels included. Where clinically necessary we use the terms ‘men’ and ‘women’ or ‘male’ and ‘female’. For example, we do so when talking about parts of the body or mentioning statistics or research about who is affected. Our aims are for our information to be as clear and relevant as possible for everyone.

You can read more about how we produce our information here.

Reviewed: 30 June 2018
Reviewed: 30/06/2018
Next review: 30 June 2021
Next review: 30/06/2021

This content is currently being reviewed. New information will be coming soon.