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.
