Ultimately, mesothelioma cannot be diagnosed without a biopsy, a sample of tissue that can be evaluated and recognized as mesothelioma. The biopsy will be taken in whatever way is easiest for each patient, which depends on where the cancer is growing.
If the patient needs fluid removed from the pleural space because he or she is having trouble breathing, the fluid can be sent for analysis. Sometimes there are mesothelioma cells in the fluid. This is usually not enough for the diagnosis but can get the doctors looking in the right direction.
Similar tests can be done for mesothelioma in the abdominal cavity. Removing fluid is called a paracentesis. Fluid can also be removed from the pericardial sac around the heart.
Some doctors will try and biopsy the pleura at the same time as when they are removing fluid. This again may yield some mesothelioma cells but is not usually enough.
There are many ways to try and get directly to the tumor to remove cells. If the tumor is growing into any of the main airways in the lung, doctors can do bronchoscopy to see the tumor and biopsy it. A bronchoscope is a long fiberoptic tube which can be passed into the bronchial tree. If the tumor can be seen, a biopsy can be taken. However, most mesotheliomas cannot be accessed this way.
A needle biopsy involves passing a long hollow needle into the lung between ribs. The place to position the needle can be aided by CT scan images. This procedure can be done on an outpatient basis. However, there is not always enough tissue obtained. There is also the possibility that the needle can cause the lung to collapse. This is treated by a suction tube placed into the pleural space.
Most of the time, these procedures do not yield sufficient tissue for diagnosis. The patient’s tumor must be visualized with a thorascope, a fiberoptic scope similar to a bronchoscope. A thorascope also has a videocamera on the end to guide the doctor doing the procedure. Patients will usually be in a surgical suite under general anesthesia. A cut is made in the chest wall, and the thorascope is passed in to look at the area between the chest wall and lungs. This may mean more than one cut to place the thorascope as well as to pass instruments in to take the samples. When the tumor is visualized, biopsies are taken. This procedure can also include sampling lymph nodes and other areas to get an idea of tumor spread for staging purposes. This is called VATS (Video-Assisted Thoracoscopic Surgery).
A similar procedure can be used to biopsy a mass in the pericardium.
When this is done to look for a tumor in the abdomen, it is called laparoscopy. This is also assisted by a videocamera. Sometimes more than one opening is needed in the abdomen.
If scans show that the tumor has probably spread to lymph nodes in the middle of the chest, a procedure called a mediastinoscopy is usually done. Mediastinoscopy is performed under general anesthesia in an operating room. A fiberoptic tube is passed in through an incision above the breast bone. The scope enters the area behind the breast bone. Using special instruments, the lymph nodes can be sampled to see if there is mesothelioma present in them.
If none of these less-invasive procedures have yielded enough tissue, doctors may have to remove specimens surgically. This means opening the chest cavity (thoracotomy) or abdominal cavity (laparotomy) to directly visualize the tumor and take pieces for study.
Once tissue had been obtained, there are multiple tests to be performed, and many different ways to look at the cells. There are various stains that can be placed on the tissue, which will then be looked at under the microscope by a pathologist. Sometimes an electron microscope will be needed to evaluate the small differences that can be found between mesothelioma and other cancers. There are other tests that can be done on the cells looking at DNA and also looking at specific proteins that will help confirm the diagnosis of mesothelioma.
Dr. Kaplan
