Types of mesothelioma

There are different types of mesothelioma. Here we provide information about pleural mesothelioma, and peritoneal mesothelioma, as well as rarer types.

The mesothelium

Mesothelioma is a cancer of the mesothelium. This is a thin lining (membrane) that covers the outer surface of many of our organs. The mesothelium in the chest is called the pleura. The mesothelium in the abdomen is called the peritoneum.

Pleural mesothelioma is much more common than peritoneal mesothelioma.

Pleural mesothelioma

The lungs sit within the chest, on either side of the heart. They supply oxygen to the organs and tissues of the body.

The lungs are covered by a lining called the pleura, which has two layers. The inner layer covers the lungs. The outer layer lines the ribcage and a sheet of muscle called the diaphragm. The diaphragm separates the chest from the tummy (abdomen).

The pleura produces a small amount of fluid. This fluid acts as a lubricant, which allows the lungs to move in and out smoothly and helps you to breathe easily.

Mesothelioma in the pleura starts as tiny lumps (nodules) that are usually spread throughout the pleura. These eventually grow together, causing the layers of the pleura to become thicker. This means the lungs and chest cannot move as freely, causing you to feel breathless. Fluid may also collect between the two layers of the pleura. This is called a pleural effusion.

The illustration shows the lungs in the chest. It shows the windpipe (trachea) coming down from the neck into the chest. About halfway down the chest, the windpipe divides into two tubes. One tube goes into the left lung. The other tube goes into the right lung. There are ribs around the outer side of each lung. Underneath the lungs, and going across the width of the body, is a muscle called the diaphragm.   Surrounding each lung is a thin lining (membrane), which has two layers. This is called the pleura. The layer closest to each lung is called the inner pleura. The layer which lines the chest wall is called the outer pleura. There is a small space between the two layers of the pleura. This space is called the pleural cavity.  There are groups of pea-sized lymph nodes in the chest. They are connected to each other by fine tubes. The lymph nodes are close to the windpipe. There are also lymph nodes on each side of the neck and in the shoulder area.

Peritoneal mesothelioma

The organs in the tummy (abdomen) are covered by a lining (membrane) called the peritoneum. It has an inner and outer layer. The inner layer covers the organs in the abdomen. The outer layer lines the abdominal wall.

The peritoneum helps protect the organs in the abdomen and keeps them in place. This is shown as the thick line surrounding the abdominal organs in the illustration opposite. When mesothelioma develops in the peritoneum, it causes the layers of the peritoneum to thicken. Fluid may also collect between the two layers. This is known as ascites.

The image shows a side view of a female body from below the chest down to the upper thigh. It shows the structures and organs in the abdomen and pelvis. There are three small openings into the pelvis between the legs. The opening closest to the back of the body is called the anus. It leads up into a tube shaped space called the back passage or rectum. The opening closest to the front of the body leads up through a short narrow tube called the urethra. This leads into a rounded hollow organ called the bladder. The opening in the middle leads through a longer tube called the vagina. This leads into a hollow organ with thick walls called the womb or uterus. The lowest part of the womb is highlighted where it meets the vagina. The highlighted area is called the cervix. At the top of the womb, a thin short tube is shown leaving the womb. This is a fallopian tube. It leads to a small solid oval organ. This is an ovary.  The womb sits behind and over the bladder. Above the bladder and womb, a large space is shown. This space fills the front half of the body. Most of the space contains an irregular bundle of thick tubing. This is the bowel. Above the bowel is a round hollow organ called the stomach. Above the stomach is a large solid organ called the liver. A thin lining is shown covering the walls of the space. The lining also covers the surfaces of the liver, stomach, bowel, bladder and womb. This lining is the peritoneum. A long flap of tissue is shown hanging down in the space in front of the bowel. This is the omentum. A line of connecting bones are shown following the curve of the back down. These are the spine. The bones come to a point behind the rectum.

Rare types of mesothelioma

Very rarely, mesothelioma may develop in the outer lining of other organs. This includes the heart (pericardial mesothelioma) or the testes (testicular mesothelioma).