PERITONEAL MESOTHELIOMA
Many of the organs in the abdomen are enveloped by a thin membrane
of mesothelial cells, known as the peritoneum.
Peritoneal mesothelioma is a tumor of this membrane. Its only known
cause in the U.S. is previous exposure to asbestos, but it can be many
years after exposure before the disease appears. Peritoneal
mesotheliomas account for about one-fifth of all mesotheliomas.
Like pleural mesothelioma, peritoneal mesothelioma can be either
benign or malignant. This discussion is only about malignant peritoneal
mesothelioma.
Mesothelioma is sometimes diagnosed by coincidence, before any
symptoms have appeared. For example, the tumor is sometimes seen on a
routine abdominal x-ray for a check-up or before surgery.
When the symptoms of peritoneal mesothelioma appear, they typically
include abdominal pains, weakness, weight loss, loss of appetite,
nausea, and abdominal swelling. Fluid often accumulates in the
peritoneal space, a condition known as ascites. Over time the wasting
symptoms can become more and more severe.
The growing tumor can exert increasing pressure on the organs in the
abdomen, leading to bowel obstruction and distention. If the tumor
presses upward, it can impair breathing capacity. If the tumor pushes
against areas with many nerve fibers, and the bowel distends, the amount
of pain can increase.
X-rays and CT scans are, typically, the first step towards detecting
peritoneal mesothelioma. The actual diagnosis is typically achieved by
obtaining a piece of tissue. The medical procedure of looking at the
peritoneum is known as a peritoneoscopy. It is a hospital procedure and
requires anesthesia. If an abnormality is seen, the doctor will attempt
to obtain a tissue sample - this is known as a biopsy. The tissue sample
will be examined by a pathologist who makes a diagnosis using
microscopic analysis of specialized stains.
There are at least two explanations for how asbestos fibers can get
into the peritoneum. The first is that fibers caught by the mucus of the
trachea and bronchi end up being swallowed. Some of them lodge in the
intestinal tract and from there they can move through the intestinal
wall into the peritoneum. The second explanation is that fibers that
lodge in the lungs can move into the lymphatic system and be transported
to the peritoneum.
Medical science does not know exactly how or why, at a cellular
level, a carcinogen like asbestos causes a cell to become malignant
(cancerous.) Thus it is not known whether only one fiber can cause a
tumor to develop or whether it takes many fibers, or what the exact
conditions and predispositions are for this change to happen.
At this time there are treatments, but no known cure, for peritoneal
mesothelioma. The prognosis depends on various factors, including the
size and stage of the tumor, its extent, the cell type, and whether or
not the tumor responds to treatment.
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