The mesothelium is a layer of tissue that covers and protects your internal organs. It allows them to move smoothly against each other and other structures.

Your mesothelium appears in several areas, including your:

  • chest cavity
  • abdominal cavity
  • heart

The mesothelium is formed by mesothelial cells. They produce lubricating fluid between the inner and outer layers of the mesothelium. This lessens friction for organ movement, such as when your lungs contract for breathing.

What conditions affect the mesothelium?

A number of medical problems can affect the mesothelium, including:

Pleural effusions

Sometimes called “water on the lungs,” pleural effusions are an abnormal buildup of excess fluid in the cavity between the two layers outside your lungs, known as the pleural mesothelium.

Causes of pleural effusions include:

If a pleural effusion is caused by cancer, it’s considered a malignant pleural effusion. According to the National Cancer Institute, the cancers most likely to cause malignant pleural effusions are:

Symptoms of pleural effusions include:

Abdominal adhesions

An abdominal adhesion is scar tissue on organs in the abdomen. These bands of scar tissue can cause organs to stick to the wall of the abdomen or to each other.

The most common cause of adhesions is handling and shifting of abdominal organs during a surgical procedure. They can also form in people with peritonitis and endometriosis.

While most abdominal adhesions don’t result in noticeable symptoms, if an adhesion has caused intestinal obstruction, symptoms might include:


If a noncancerous tumor forms in the mesothelium, it’s referred to as benign mesothelioma or solitary fibrous tumor.

Malignant mesothelioma is an aggressive type of cancer characterized by malignant tumors in the mesothelium.

Pleural mesothelioma — which affects the area around the lungs — is the most common. The primary risk factor for this type is exposure to asbestos. Other factors could include genetics and radiation treatments for other cancers.

Symptoms of pleural mesothelioma include:

  • chest pain under your rib cage
  • painful coughing and coughing up of blood
  • shortness of breath or wheezing
  • abnormal lumps of tissue under the skin on your chest
  • weight loss

Peritoneal mesothelioma of the abdomen, pericardial mesothelioma of the tissue around the heart, and tunica vaginalis mesothelioma of the testicles are all rare.

Symptoms of peritoneal mesothelioma include:

  • abdominal pain or swelling
  • abnormal lumps of tissue in the abdomen
  • weight loss

Symptoms of pericardial mesothelioma include breathing difficulty and chest pains.

Symptoms of tunica vaginalis mesothelioma include swelling and a lump on a testicle.

The takeaway

The mesothelium is a part of your body you rarely think about. In fact, many don’t know that it exists or that it plays an important role in protecting your internal organs.

Most people learn about the mesothelium when they experience a medical issue that affects it. If you notice symptoms of any of the conditions listed above, make an appointment with your doctor for a full diagnosis.