What is Peritoneal Mesothelioma?
Peritoneal Mesothelioma is a malignant cancer that is much rarer than Pleural mesothelioma. About 100 – 500 cases are diagnosed in the USA each year, which is about 25% – 30% of all mesothelioma cases.
Results of diagnosis are approximately 54.7% in male versus 45.3% in females, with an average age of 65 – 69 (Source: SEER – Surveillance, Epidemiology, and End Results).
Symptoms for Peritoneal mesothelioma surface to life 20 – 30 years after Asbestos exposure, as opposed to Pleural mesothelioma where symptoms surface to life after 30 – 40 years.
Peritoneal mesothelioma attacks the abdominal lining or Peritoneum of the lungs, and thus is also known as abdominal mesothelioma.
The peritoneum insulates organs of the abdomen and its primary purpose is for protection. The image on the left is of the peritoneum consisting of 2 parts; visceral and parietal peritoneum.
The function of the visceral peritoneum is to cover internal abdominal organs and it makes up most of the outer layer of the intestinal tract. The parietal peritoneum (outer layer) on the other hand insulates the abdominal cavity and is attached to the abdominal wall.
The space between these two layers is known as the peritoneal cavity, filled with a 50ml serous fluid that allows the 2 layers to freely slide and glide over each other. Another purpose for the serous fluid is to help the intestines move food freely throughout the body.
Cancerous cells force the peritoneal cavity to overproduce the serous fluid causing an excessive buildup of fluids in the abdominal cavity. This is also known as ascites.
Development of Peritoneal Mesothelioma
Just like Pleural mesothelioma, the single most important factor for development of Peritoneal mesothelioma is exposure to Asbestos.
The process of how tissues in the lungs become malignant or cancerous (the carcinogenic process) is not fully understood by doctors yet. After inhalation of asbestos fibers at workplaces, they cannot be removed by the body’s immune system because of their durability.
Over a period of time, they cause chronic inflammation of cells in the lungs and develop a fibrosis that stop the peritoneum from functioning properly and protecting abdominal organs.
The main difference between pleural & peritoneal mesothelioma is how asbestos fibers penetrate into the peritoneum. Scientists predict there are 3 ways this can happen:
- Inhaled asbestos fibers are transported through the lymphatic system to the peritoneal cavity (space between the parietal & visceral peritoneum layers). The image above is of the lymphatic system where the black markers are primary translocators of asbestos fibers into the lungs, while the white markers are secondary translocators of asbestos fibers. The diagram shows how asbestos fibers can travel through the lymphatic system starting from the alveolar space or the pulmonary cap into the pleural space.
- Asbestos fibers entered the body through foods & drinks that asbestos workers had whilst on the job. Asbestos dust & fibers in the air is common among workplaces such as factories, shipyards & metal works.
- Asbestos fibers are carried into the abdominal cavity & lining by being broken down into smaller pieces and transported through the bloodstream.
Diagnosis and Staging of Peritoneal Mesothelioma
Diagnosis of Peritoneal mesothelioma is very difficult, if not impossible. Computed Tomography (CT) scans are commonly used to distinguish between the two types of peritoneal mesothelioma; “dry” or “wet”.
What’s interesting is that the image that CT scans produce can vary significantly. In the “dry” type of photos, CT scans reveal small localized masses of tumors with no fluids (ascites). In the “wet” type, CT scans reveal widespread masses of tumors with presence of fluids (ascites).
Doctors can then order a removal of fluids from the abdomen via a process called paracentesis. The image on the left is of the Pelvis showing large volumes of free ascites (fluids in the lungs or abdomen). These fluids can then be removed via a process called pleural effusions.
As for Staging Peritoneal mesothelioma, there is no set system that can stage the extent of how far the tumor has spread. However, it is staged using the TNM system which is the most common cancer staging system. TNM stands for tumor (T), lymph nodes (N) and metastases (M). Peritoneal mesothelioma can also be detected in ‘Stages’.
- Stage 1: Shows a tumor or wound that that can be completely removed from the surface of the lungs.
- Stage 2: Shows the tumor contained in the abdominal cavity or in the peritoneal cavity where some portion of it can be removed but not all.
- Stage 3: Shows tumor in the abdominal cavity where organs such as the liver or colon are damaged.
- Stage 4: Shows tumors that have extended outside the abdominal cavity.
Symptoms of Peritoneal Mesothelioma
Symptoms of Peritoneal mesothelioma are closely associated with symptoms of other diseases such as gallbladder problems, hernia or pelvic mass. Here is a list of the typical symptoms:
- Weight loss
- Abdominal mass and abdominal pain
- Distention (spreading & stretching in all directions) of the abdomen
- Fluids in the abdomen (ascites)
- Weight loss
- Digestion problems
When a doctor diagnoses peritoneal mesothelioma, usually the tumor has grown to very advanced stages because its symptoms are easily associated with symptoms of other common diseases.
Advanced stages of peritoneal malignant mesothelioma often means multiple tumors have invaded the peritoneum and the cancer has spread (metastasized) to other areas such as the lungs, lymph nodes, and the heart.
Treatment of Peritoneal Mesothelioma
Treatment options available for Peritoneal mesothelioma are similar to what is available for Pleural mesothelioma. Options include Magnetic Resonance Imaging (MRI), X-Rays or Computed Tomography (CT) scans.
There is no cure for peritoneal mesothelioma however, it does provide a longer life and a better prognosis than pleural mesothelioma.
After being diagnosed with pleural mesothelioma, a patient can expect to live for an average of 1 year to 16 months. On the other hand, a patient diagnosed with Peritoneal mesothelioma can expect to live for another average of 2 – 5 years.