Peritoneal Cancer

What is peritoneal cancer?

Peritoneal cancer refers to cancer that develops within or more commonly, has spread to the peritoneum from other organs within the abdomen (known as peritoneal metastases). The peritoneum is the tissue that lines and protects the organs in the abdomen such as the stomach, bowel and ovaries.

The peritoneum is made of epithelial cells, which is the same type of tissue that lines the ovaries. This means that peritoneal cancer often acts and looks like ovarian cancer, from causing similar symptoms to requiring the same types of treatments.

Whilst primary tumours of the peritoneum are very rare, with women more likely than men to develop cancer in the peritoneum, spread to the peritoneum from other abdominal cancers, such as stomach, colon and ovarian cancers, is very common.

Stages of peritoneal cancer

Primary peritoneal cancer can be described in stages depending on how early or advanced the cancer is. Primary peritoneal cancer is often diagnosed at a more advanced stage – Stage III or Stage IV, because the symptoms in the early stages are often missed.

Primary peritoneal cancer is staged using the same guidelines as ovarian cancer, known as the FIGO (International Federation of Gynaecology and Obstetrics) system. These stages give an indication of how little to how much the cancer has progressed.

As the staging of primary peritoneal cancer can be complex, it is important to discuss your individual diagnosis and stage with your specialist.

  • Stage IIIA – the cancer has spread to the lymph nodes outside of the peritoneum, or to the surface of the peritoneum outside of the pelvis
  • Stage IIIB – the cancer has grown into the peritoneum outside the pelvis and the cancer in the peritoneum is 2 cm or smaller. The cancer may also have spread to lymph nodes outside the peritoneum
  • Stage IIIC – the cancer has spread to the peritoneum outside the pelvis and the cancer in the peritoneum is larger than 2 cm. The cancer may also have spread to lymph nodes outside the peritoneum or to the surface of the liver or spleen
  • Stage IVA – the cancer has caused a build-up of fluid in the lungs (pleural effusion)
  • Stage IVB – the cancer has spread to areas outside of the abdomen, such as the lungs or inside of the liver or spleen

Peritoneal metastases, or cancers that have spread from other areas of the body to the peritoneum, are considered advanced cancers and are classified as Stage IV in most instances based on the staging of their primary cancer type.

Signs and symptoms of peritoneal cancer

Primary peritoneal cancer and peritoneal metastases can be difficult to detect as symptoms can be vague and often attributed to other common conditions. These may include:

Bloated or swollen stomach

that doesn’t go away

Loss of appetite

Feeling full quickly

when eating


in the abdomen or back

Changes in urinating

more frequent or urgent need to pass urine


between periods or after menopause

Changes in bowel habits

such as constipation or diarrhoea

Weight gain or loss

that can’t be explained by diet and exercise-related factors


Whilst these symptoms may be due to other causes besides peritoneal cancer, it is always important to see your doctor if they persist.

Treatment for peritoneal cancer

Frequently asked questions

How common are peritoneal metastases?

Peritoneal metastases are common for a number of different primary cancer types, including:

  • Ovarian cancer – 46% of ovarian cancer patients develop peritoneal metastasis
  • Colorectal cancer – 7% of cases develop synchronous peritoneal metastasis
  • Gastric carcinoma – Peritoneal metastasis accounts for 14% of advanced gastric carcinoma presentations
  • Cancers located outside of the abdomen – Peritoneal metastasis in cancers located outside of the abdomen account for only 10% of cases, primarily metastatic breast cancer (41%), lung cancer (21%), and malignant melanoma (9%)
How is peritoneal cancer diagnosed?

There are many different tests that are used to diagnose peritoneal cancer. This may include an internal examination, ultrasound or CA125 blood test, followed by further tests such as a CT scan, biopsy, peritoneal fluid analysis or genetic testing to identify genetic mutations that are linked to cancer.

What are the risk factors for primary peritoneal cancer?

While similar to ovarian cancer, primary peritoneal cancer can occur even when the ovaries have been removed. As this type of cancer is very rare, the risk factors that increase the chance of peritoneal cancer developing are not well known. However, some risk factors may include:

  • Age
  • Genetics – having a mutation in the BRCA1 and BRCA2 genes can increase your risk
  • Family history of ovarian cancer or peritoneal cancer
  • Hormone replacement therapy
  • Being overweight or obese
  • Endometriosis
How can primary peritoneal cancer be prevented?

There are unfortunately no known methods to definitively prevent primary peritoneal cancer. You should consider general sensible measures such as:

  • Quitting smoking
  • Limiting alcohol intake
  • Having a healthy, balanced diet, with a variety of fruits and vegetables
  • Maintaining a healthy weight


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