Peritoneal mesothelioma is a relatively rare form of malignant mesothelioma, making up twenty to twenty five percent of diagnosed mesothelioma cases. This type of mesothelioma affects the cells of the peritoneal mesothelium, also known as the peritoneum, which is the membrane lining the abdominal cavity wall. In this area of the body the mesothelium membrane also supports and protects organs in the abdomen. The peritoneum is made up of two layers, called the visceral and parietal layers. The parietal layer is an outer layer that covers the abdominal cavity, while the visceral layer covers internal organs and the intestinal tract.
All types of mesothelioma are caused by the presence of microscopic asbestos fibers which most often enter the human body by inhalation. These fibers are given off by deteriorating or torn asbestos material, they can float in a dust cloud for a long period, and they are unnoticed when inhaled. That is how they enter the lungs and cause pleural mesothelioma in the lung lining. It is less clear how these fibers make their way to the abdominal cavity.
It is possible that they are ingested in some fashion and work their way through the intestinal system just as they pass through the lungs to the outer layer. It has also been suggested that they pass through the body via the lymphatic system. In any case, when they become embedded in the peritoneum they can cause an assortment of symptoms and eventually cause the development of abnormal, malignant cells.
Impact of Asbestos Fibers on the Peritoneum
One of the most common symptoms of peritoneal mesothelioma is ascites, or the accumulation of excess fluid in the abdominal cavity. This symptom can be assigned to a number of more common conditions, from liver disease to intestinal problems. Just as with pleural mesothelioma, the nature of the symptoms can be misleading. One study cited a mean period of 122 days from the presentation of symptoms to diagnosis.
Once in the peritoneum, asbestos fibers cause changes in peritoneal cells that cause them to divide without restraint, causing the peritoneal layers to thicken. The growth of cancer cells puts pressure on internal organs, and this pressure is increased by the fluid buildup. The accumulation of pressure can sometimes cause adjacent organs to begin to malfunction, further complicating diagnosis. Intestinal obstruction can occur, as can emergency surgery due to inflammatory lesions. Thrombosis in the veins and hypoglycemia are common symptoms.
Despite the evidence of some sort of highly intrusive affliction, CT scans and radiology exams won't result in a firm diagnosis. A precise diagnosis based on imaging alone is not possible. Peritoneal mesothelioma may consist of a single tumor, diffuse small tumors, or a combination along with benign calcified nodules. It is not a disease that can easily be addressed surgically.
Symptoms of Peritoneal Mesothelioma
The section above discusses many of the more severe symptoms of peritoneal mesothelioma. When a patient is first seen, however, the collection of complaints may include some very common physical conditions that can be attributed to several different ailments. A brief list of common initial symptoms:
- Weight loss
- Fever or night sweats
- Pain or swelling in the abdominal area
- Obstruction of the small or large intestine
- Edema or thrombosis in the legs
Peritoneal Mesothelioma Diagnosis
Once a physician has determined that this rare disease may be involved in the case, diagnostic measures are multifaceted. While the use of imaging equipment cannot produce a complete diagnosis, it can produce evidence of a mass growing on one of the peritoneal mesothelium surfaces, or show an accumulation of small irregularities that may be tumors or plaques.
Biopsy is a common choice at this juncture, often performed along with a laparoscopy in order to allow for more accurate observation of any internal masses. Protein markers found in blood samples that are evidence of one of the two types of mesothelioma cells – epithelial or sarcomatoid – are used in some pathology labs.
Treatment for Peritoneal Mesothelioma
Despite the commonly diffuse nature of peritoneal mesothelioma, surgical resection is still the best option if the disease is at the stage where most or all of the malignant tissue can be removed. In situations where all of the diseased tissue cannot be removed, as much as possible is taken and the procedure is called "debulking." Where possible, "intracavity" chemotherapy is undertaken during the surgical process to more precisely target the malignant areas remaining within the abdomen.
For most patients with peritoneal mesothelioma that has metastasized to one of the nearby organs treatment is palliative, and is designed reduce the rate at which the cancer spreads. If the surgery is relatively successful and the following therapy has some effect the survival time can stretch beyond two years. For partial resections the survival period is far shorter.
In cases where surgery and chemotherapy are not suitable treatment options, palliative treatment is used to provide symptomatic relief; however, such treatments cannot slow the progression of the cancer. These types of treatments are used simply to manage pain and provide relief from symptoms such as the build-up of fluid in the peritoneal cavity.
It is difficult to find survival period figures that reflect the results of a large sample. However the consensus seems to be that post-surgical survival times for peritoneal mesothelioma is better, on the average, than for pleural mesothelioma. A study done in the UK followed seventeen patients over a period from 1998 to 2007 who underwent surgery for resection of peritoneal mesothelioma, followed by a thorough chemotherapy program. Eight of the patients had a partial resection, or debulking, of malignant tissue and eight had a full resection. The average survival period for those with a partial removal of cancerous tissue was one year, while for the patients with a full resection it was 3.7 years. Either figure is well beyond the survival rates for pleural mesothelioma patients.
- Malignant Peritoneal Mesothelioma, PubMed,NIH, V. De Pangher Manzini, 2005
- Peritoneal Mesothelioma: A Review, PubMed,NIH, Dept. of Surgical Sciences, University of Padua Medical School, 2007
- Peritoneal Mesothelioma: A Review, p.5
- Cytoreductive Surgery and Intraperitoneal Chemotherapy for Peritoneal Mesothelioma, PubMed, NIH, Pseudomyxoma Peritonei Centre, Hampshire, UK, 2008.