If there is a reason to suspect you may have a
mesothelioma, the doctor will use one or more methods to find out if
the disease is really present.
Medical history and
physical examination:
A complete medical history (interview) is taken to
check for risk factors and symptoms. This will include questions to
determine if you have been exposed to asbestos.
A physical exam will provide information about signs
of mesothelioma and other health problems. Patients with pleural
mesothelioma (mesothelioma of the chest) often have pleural effusion
(fluid in their chest cavity) caused by the cancer. Ascites (fluid in
the abdominal cavity) in cases of peritoneal mesothelioma, and
pericardial effusion (fluid in the pericardium) in cases of
pericardial mesothelioma can also be detected during a physical exam.
Imaging tests:
A chest x-ray may show irregular thickening of the
pleura, pleural calcifications (mineral deposits), lowering of the
lung fissures (spaces between the lobes of the lungs), and fluid in
the pleural space. These findings suggest asbestos exposure leading to
the development of a mesothelioma.
Imaging studies such as x-rays, computed tomography
(CT) scans, and magnetic resonance imaging (MRI) scans will help
determine the location, size, and extent of the cancer. The CT scan
uses a rotating x-ray beam to create a series of pictures of the body
from many angles. A computer combines these pictures to produce
detailed cross-sectional images of a selected part of the body. To
highlight details on the CT scan, you may be asked for permission to
have a harmless dye injected into a vein. MRI uses magnetic fields
instead of x-rays to create images of selected areas of the body. As
with the CT scan, a computer generates a detailed cross-sectional
image.
Tests of fluid and
tissue samples:
In patients with a pleural effusion, a sample of this
fluid can be removed by inserting a needle into the chest cavity. A
similar technique can be used to obtain abdominal fluid and
pericardial fluid. The fluid is then tested to show its chemical make
up and viewed under a microscope to determine whether cancer cells are
present.
A tissue sample of a pleural or pericardial tumor can
be obtained using a relatively new technique called thoracoscopy. A
thoracoscope (telescope-like instrument connected to a video camera)
is inserted through a small incision into the chest. The doctor can
see the tumor through the thoracoscope, and can use special forceps to
take a tissue biopsy. Similarly, laparoscopy can be used to see and
obtain a biopsy of a peritoneal tumor. In this procedure, a flexible
tube attached to a video camera is inserted into the abdominal cavity
through small incisions on the front of the abdomen. Fluid can also be
collected during thoracoscopy or laparoscopy.
Surgery, either a thoracotomy (which opens the chest
cavity) or a laparotomy (which opens the abdominal cavity), allows the
surgeon to remove a larger sample of tumor or, sometimes, to remove
the entire tumor.
For patients who might have pleural mesothelioma, the
doctor may also do a bronchoscopy. In this procedure a flexible
lighted tube is inserted through the mouth, down the trachea, and into
the bronchi to see if there are other masses in the airway. Small
samples of abnormal-appearing tissue can be removed for testing.
The patient may also have a mediastinoscopy. A lighted
tube is inserted under the sternum (chest bone) at the level of the
neck and moved down into the chest. Mediastinoscopy allows the surgeon
to view the lymph nodes in this area and remove samples to check for
cancer. Lymph nodes are bean-sized collections of immune system cells
that help the body fight infections and cancers. Cancers arising in
the lung often spread to lymph nodes, but mesothelioma rarely do this.
Tests of lymph nodes can give the doctor information on whether a
cancer is still localized or if it has started to spread, and can help
distinguish lung cancer from mesothelioma.
It is often hard to diagnose mesothelioma by looking
at the cells from the fluid around the lungs, abdomen or heart. It is
even hard to diagnose mesothelioma with tissue from biopsies. Under
the microscope, mesothelioma can look like several other types of
cancer. For example, pleural mesothelioma may resemble some types of
lung cancer and peritoneal mesothelioma may resemble some cancers of
the ovaries. For this reason, special laboratory tests are often done
to help distinguish mesothelioma from some other cancers. These tests
often use special techniques to recognize certain markers (types of
chemicals) known to be contained in mesothelioma. Different markers
are present in cancer of the lung or ovary. The electron microscope
can sometimes be helpful in diagnosing mesothelioma. This microscope
can magnify samples more than 100 times greater than the light
microscope which is generally used in cancer diagnosis. This stronger
microscope makes it possible to see small parts of the cancer cells
that distinguish mesothelioma from other types of cancer.
The diagnosis of mesothelioma presents problems
primarily initially in the distinction between mesothelioma and other
forms of cancer such as adenocarcinoma or benign, non-cancerous
pleural inflammation. The best diagnostic tools at the moment remain
the open pleural biopsy performed during thoracoscopy. This procedure
also allows for direct visualization of the inside of the chest, and
information of involvement of other organs and extension of disease.
Other procedures with lower yields are CT guided pleural biopsy, or
blind pleural biopsy. In addition to the gross appearance of the
tumor, pathologists often rely on a panel of histochemical and
immunohistochemical stains to diagnose or exclude mesothelioma.
Currently markers linked to prognosis of mesothelioma are under study,
but have not been validated for the general use.
