While 70% of mesothelioma cases occur in and around the lungs (pleural mesothelioma), approximately 30% of all mesothelioma cases occur in the abdomen. Mesothelioma occurring in the abdomen is known as peritoneal mesothelioma.
The peritoneal cavity is a fairly large space which houses the liver, intestines, and other organs of the abdomen. The peritoneum is the covering on the walls of the abdomen (parietal peritoneum) and over the organs themselves (visceral peritoneum). Peritoneal mesothelioma occurs in either the parietal or visceral peritoneum, but many cases occur as a result of mesothelioma that has spread from the lungs (pleura).
Unlike breathing problems caused by pleural mesothelioma, peritoneal mesothelioma does not usually cause symptoms until the disease is advanced. The tumor is also very fast growing. The combination of late diagnosis and rapid growth rate combine to make peritoneal mesothelioma a very deadly disease. In fact, up until ten years ago, peritoneal mesothelioma was considered universally fatal. Even with aggressive treatment, most people with peritoneal mesothelioma will die from the disease.
Symptoms of Peritoneal Mesothelioma
The symptoms of peritoneal mesothelioma can vary from patient to patient. Abdominal pain is the most common initial complaint and will be the reason that patients with peritoneal mesothelioma seek medical treatment about one third of the time. Another third of patients will seek medical attention because their abdomen is increasing in size. The progressive abdominal widening takes place only in the stomach and not in other body areas as would occur with weight gain or fat deposition. Since peritoneal mesothelioma is a cancer, the increased abdominal girth may occur despite losing weight and wasting overall. Five percent of the time patients will report both an increase in abdominal girth and abdominal pain at the first office visit.
A peritoneal mesothelioma may be diagnosed during an evaluation of a new hernia, that is, a place where the contents of the abdomen are poking into a space that they do not normally enter. It is not unusual for the cancer to cause a decrease in appetite. Even though the peritoneal mesothelioma may not occur in the lungs, if the peritoneum near the bottom of the lungs is affected, the tumor can cause shortness of breath as it presses on the diaphragm.
In advanced disease, a mass may be felt through the skin by pressing on the abdomen. Also in advanced peritoneal mesothelioma, the bowel may become obstructed if the tumor presses directly on the intestine. Symptoms of bowel obstruction include constipation, bloating, and stomach pain. If the tumor invades into the intestine itself, it can cause bleeding in the stool. If the bowel is perforated by the tumor, emergency surgery but may be required since this condition can lead to a very serious infection of the abdomen and blood.
In addition to the symptoms caused mainly by the physical mass of the tumor, there are also a number of cancer-related symptoms that can occur with peritoneal mesothelioma. These symptoms are collectively known as paraneoplastic syndromes. Among the paraneoplastic syndromes that may occur are hypercoagulability, night sweats, thrombocytosis, hypoglycemia, and liver disease. Hypercoagulability is a state in which the blood tends to clot too much. This could lead to blood clots within the blood vessels. Clots within blood vessels lead to heart attack, stroke, and deep vein thrombosis (DVT), among other conditions. Thrombocytosis is related to hypercoagulability in that it is a condition in which platelets (thrombocytes) are present in abnormally high concentrations in the blood. Thrombocytosis can contribute to abnormal clot formation as well. Hypoglycemia is a state of low blood sugar and can cause dizziness, confusion, and altered consciousness.
Diagnosis of Peritoneal Mesothelioma
The diagnosis of peritoneal mesothelioma generally includes laboratory blood work and radiological imaging. Once the diagnosis is strongly suspected, surgery is usually required to confirm the diagnosis and provide treatment. Peritoneal mesothelioma is notoriously difficult to diagnose and, on average, it takes four months from first appointment to a definitive diagnosis.
Standard laboratory tests are usually not helpful in the diagnosis of peritoneal mesothelioma but are routinely performed. Two of the changes that may be apparent from routine blood work are a high thrombocyte (platelet) count and/or elevated serum calcium. These tests are not specific to peritoneal mesothelioma but do increase the suspicion of a cancer diagnosis.
Cancer tumor markers may be more helpful than standard lab tests, if they are considered by the physician. Most patients with peritoneal mesothelioma will have elevated levels of a tumor marker called serum mesothelin-related protein (SMRP) in the blood. Other tumor markers may be checked as well, though they are less specific to peritoneal mesothelioma.
In addition to blood work, most patients will undergo CT (computerized tomography) of their chest, abdomen, and pelvis as part of a cancer workup. Sadly, the changes that occur in peritoneal mesothelioma do not easily show up on these tests. In fact, given the current state of technology, it is not possible to make a definitive diagnosis of peritoneal mesothelioma by CT alone. CT imaging may help focus the possible causes for symptoms and rule out others. It may also help guide a future biopsy. It is not clear at this point whether ultrasound or MRI would be better for diagnosis of this illness than CT.
The only way to make an accurate, definitive diagnosis of peritoneal mesothelioma is to obtain and analyze cells from the potential tumor. One way to do this is by inserting a needle into the abdomen and drawing off cells that happen to be floating around. This is not a very useful approach in general and most doctors spare the patient the time and discomfort of this procedure. If the tumor can be reached by a fine needle aspiration, surgery may not be required for diagnosis. Alternatively, a direct biopsy of the tissue is an excellent way to make a diagnosis of peritoneal mesothelioma, but it requires that the patient undergo a surgical procedure.
Once a sufficient sample of the tumor has been removed by one of these methods, a pathologist can subject it to a number of immunohistochemical and other specialized tests. The appearance of the prepared biopsy under a microscope is used to make the diagnosis and to determine whether the peritoneal mesothelioma is benign or malignant.
Treatment of Peritoneal Mesothelioma
Radical resection should be attempted whenever possible since this treatment approach leads to the best outcomes. Radical resection is technically challenging and involves removal of a large portion of the abdomen and peritoneum. Since much of the abdomen and its contents are required for life, the entire peritoneal mesothelioma is rarely removed in this surgery. Surgery that is aimed at removing as much of the tumor as possible while the knowledge that removal of the entire cancer is not possible is called cytoreductive surgery.
Cytoreductive surgery combined with hyperthermic chemotherapy has increased survival of patients with peritoneal mesothelioma. In this approach, chemotherapeutic drugs are heated and placed directly in the abdominal cavity during or after cytoreductive surgery. The heat of the chemotherapy drugs is believed to slow the growth of tumor cells. In addition, the use of chemotherapeutic agents directly on the tumor allows for much higher concentrations of the cancer-killing drug to be placed on the tumor than could be achieved if the drug was administered in a vein.
Various intravenous and oral chemotherapy regimens have been tried and do have a place in peritoneal mesothelioma treatment. Depending on the regimen used, survival may be increased with the use of these agents.
Prognosis for Peritoneal Mesothelioma Patients
Until recently, the median survival after a diagnosis of peritoneal mesothelioma was one year. With cytoreductive surgery and hyperthermic chemotherapy approximately 50% of patients can survive five years after diagnosis. There are various prognostic indicators that can be used to provide a more accurate estimate of survival from peritoneal mesothelioma. Even with optimal treatment, peritoneal mesothelioma remains a highly lethal disease.
References for Informaton on this page
- Al-Shammaa HA, Li Y, Yonemura Y. Current status and future strategies of cytoreductive surgery plus intraperitoneal hyperthermic chemotherapy for peritoneal carcinomatosis. World J Gastroenterol 2008;14:1159-1166.
- Bridda A, Padoan I, Mencarelli R, Frego M. Peritoneal mesothelioma: a review. MedGenMed 2007;9:32.
- Browne K, Smither WJ. Asbestos-related mesothelioma: factors discriminating between pleural and peritoneal sites. Br J Ind Med 1983;40:145-152.
- Chua TC, Yan TD, Morris DL. Surgical biology for the clinician: peritoneal mesothelioma: current understanding and management. Can J Surg 2009;52:59-64.
- de Pangher Manzini, V. Malignant peritoneal mesothelioma. Tumori 2005;91:1-5.
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