How Is Malignant Mesothelioma Diagnosed? Part -2

Positron emission tomography (PET) scan For a PET scan, you receive an injection of glucose (a form of sugar) that contains a radioactive atom. The amount of radioactivity used is very low. Cancer cells in the body are growing quickly, so they absorb large amounts of the radioactive sugar. A special camera can then be used to create a picture of areas of radioactivity in the body. The picture is not finely detailed like a CT or MRI scan, but it can provide helpful information about your whole body. A PET scan can help give the doctor a better idea of whether a thickening of the pleura or peritoneum seen on another imaging test is more likely cancer or merely scar tissue. If you have been diagnosed with cancer, your doctor may use this test to see if the cancer has spread to lymph nodes or other parts of the body. A PET scan can also be useful if your doctor thinks the cancer may have spread but doesn't know where. Some newer machines are able to perform both a PET and CT scan at the same time (PET/CT scan). This allows the doctor to compare areas of higher radioactivity on the PET scan with the more detailed appearance of that area on the CT. Magnetic resonance imaging (MRI) scan Like CT scans, MRI scans provide detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into very detailed images of parts of the body. A contrast material called gadolinium is often injected into a vein before the scan to better see details. MRI scans can sometimes help determine the exact location and extent of a tumor since they provide detailed images of soft tissues. For mesotheliomas, they may be useful in looking at the diaphragm (the thin band of muscle below the lungs that is responsible for breathing), a possible site of cancer spread. MRI scans may be a little more uncomfortable than CT scans. They take longer -- often up to an hour. You may be placed inside a large cylindrical tube, which is confining and can upset people with a fear of enclosed spaces. Newer, more open MRI machines can help with this if needed. The MRI machine makes buzzing and clicking noises that you may find disturbing. Some places will provide earplugs to help block this out. Blood tests Blood levels of certain substances are often elevated in people with mesothelioma: • osteopontin • soluble mesothelin-related peptides (SMRPs), detected with the MesoMark® test Blood tests for these substances are not used to diagnose the disease, but elevated levels may make the diagnosis more likely. Thus far, these blood tests have proven more useful in people who have already been diagnosed to follow their progress during and after treatment. If mesothelioma is diagnosed, other blood tests will be done to check the blood cell counts and levels of certain chemicals in the blood. These tests can give the doctor an idea of how extensive the disease may be, as well as how well organs such as the liver and kidneys are functioning. Tests of fluid and tissue samples A person's symptoms and the results of exams, imaging tests, and/or blood tests may strongly suggest that mesothelioma is present, but the actual diagnosis is made by removing cells from an abnormal area and looking at them under a microscope. This is known as a biopsy. It may be done in different ways, depending on the situation. Thoracentesis, paracentesis, and pericardiocentesis If you have a buildup of fluid in the body that may be related to mesothelioma, a sample of this fluid can be removed by inserting a long, hollow needle through the skin and into the fluid and removing it. Numbing medicine is used on the skin before the needle is inserted. This may be done in a doctor's office or in the hospital. This procedure has different names depending on where the fluid is: • Thoracentesis removes fluid from the chest cavity. • Paracentesis removes fluid from the abdomen. • Pericardiocentesis removes fluid from the sac around the heart. The fluid is then tested to see its chemical makeup and is looked at under a microscope to see if there are cancer cells in the fluid. If cancer cells are present, special tests can determine if the cancer is a mesothelioma, a lung cancer, or another type of cancer. Not finding any cancer cells in the fluid does not necessarily mean there is no cancer, as not all fluid may contain cancer cells. In many cases, doctors need to get an actual sample of the pleural or peritoneal tissue to determine if mesothelioma is present. Needle biopsies Suspected tumors in the chest are sometimes sampled by needle biopsy. A long, hollow needle is passed through the skin in the chest between the ribs and into the pleura. Imaging tests such as CT scans are used to guide the needle into the tumor so that a small sample can be removed to be looked at under the microscope. This procedure is also done without a surgical incision or overnight hospital stay. In some cases, the sample removed may not be big enough to make an accurate diagnosis, and a more invasive biopsy method may be needed. A possible complication of this approach is the buildup of air between the lung and the chest wall, which is known as a pneumothorax. In some cases this can lead to the collapse of part of a lung, causing shortness of breath. If this happens, it can be treated by temporarily placing a suction tube through the skin and into the chest, which will re-expand the lung. Thoracoscopy, laparoscopy, and mediastinoscopy In most cases, a tissue sample of a pleural or pericardial tumor can be obtained using a technique called thoracoscopy. Most often this is done in the operating room while you are under general anesthesia (in a deep sleep). The doctor inserts a thin, lighted tube with a small video camera on the end (a thoracoscope) through a small cut made in the chest wall to view the space between the lungs and the chest wall. (Sometimes more than one cut is made.) Using this, the doctor can see potential areas of cancer and remove small pieces of tissue to look at under the microscope. Thoracoscopy can also be used to sample lymph nodes and fluid and assess whether a tumor is growing into nearby tissues or organs. Similarly, laparoscopy can be used to see and obtain a biopsy of a peritoneal tumor. In this procedure, a flexible tube containing a small video camera is inserted into the abdominal cavity through small cuts on the front of the abdomen. If imaging tests such as a CT scan suggest that the cancer may have spread to the lymph nodes between the lungs, the doctor may do a procedure called a mediastinoscopy. This is also done in an operating room while you are under general anesthesia (in a deep sleep). A small cut is made in the front of the neck above the breastbone (sternum) and a thin, hollow, lighted tube is inserted behind the sternum. Special instruments can be passed through this tube to take tissue samples from the lymph nodes along the windpipe and the major bronchial tube areas. Cancers in the lung often spread to lymph nodes, but mesotheliomas do this less often. Tests on 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. Surgical biopsy In some cases, more invasive procedures may be needed to get a large enough tissue sample to make a diagnosis. 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. Bronchoscopic biopsy If you might have pleural mesothelioma, the doctor may also do a bronchoscopy. The doctor passes a long, thin, flexible, fiber-optic tube called a bronchoscope down the throat to look at the lining of the lung's main airways. You will be sedated for this. If a tumor is found, the doctor can take a small sample of the tumor through the tube. Testing the samples in the lab No matter which approach used to obtain them, biopsy and fluid specimens are sent to the pathology lab. There, a doctor will look at them under a microscope and do other tests to determine if cancer is present (and if so, what type of cancer it is). 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 small needle 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 look like some cancers of the ovaries. For this reason, special lab 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) contained in mesothelioma cells. • Immunohistochemistry tests look for different proteins on the surface of the cells. It can be used to tell if the cancer is a mesothelioma or a lung cancer, which can appear to start in the lining of the chest cavity. • DNA microarray analysis is a newer test that actually looks at patterns of genes in the cancers. Mesotheliomas have different gene patterns than other cancers. • Electron microscopy can sometimes help diagnose mesothelioma. The electron microscope can magnify samples more than 100 times greater than the light microscope that is generally used in cancer diagnosis. This more powerful microscope makes it possible to see the small parts of the cancer cells that distinguish mesothelioma from other types of cancer. If mesothelioma is diagnosed, the doctor will also determine what type of mesothelioma it is, based on the patterns of cells seen in the microscope. Mesotheliomas are classified as either epithelioid, sarcomatoid, or mixed/biphasic. Pulmonary function tests Pulmonary function tests (PFTs) may be done after a mesothelioma diagnosis to see how well your lungs are working. This is especially important if surgery is an option in treating the cancer. Because surgical removal of part or all of lung results in lower lung capacity, it's important to know how well the lungs are working beforehand. These tests can give the surgeon an idea of whether surgery may be an option, and if so, how much lung can safely be removed. There are a few different types of PFTs, but they all basically involve having you breathe in and out through a tube that is connected to different machines.