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Diagnosing mesothelioma is often difficult, because the symptoms are similar to those of a number of other conditions. Diagnosis begins with a review of the patient's medical history, including any history of asbestos exposure. A history of exposure to asbestos may increase clinical suspicion for mesothelioma. A complete physical examination may be performed, including x-rays, of the chest or abdomen and lung function tests. The X-ray may reveal pleural thickening commonly seen after asbestos exposure and increases suspicion of mesothelioma. A CT (or CAT) scan or an MRI is usually performed. If a large amount of fluid is present, abnormal cells may be detected by cytology if this fluid is aspirated with a syringe. For pleural fluid this is done by a pleural tap or chest drain, in ascites with an paracentesis or ascitic drain and in a pericardial effusion with pericardiocentesis. While absence of malignant cells on cytology does not completely exclude mesothelioma, it makes it much more unlikely, especially if an alternative diagnosis can be made (e.g. Tuberculosis, heart failure).
If cytology is positive or a plaque is regarded as suspicious, a biopsy is needed to confirm a diagnosis of mesothelioma. A doctor removes a sample of tissue for examination under a microscope by a pathologist. A biopsy may be done in different ways, depending on where the abnormal area is located. If the cancer is in the chest, the doctor may perform a thoracoscopy. In this procedure, the doctor makes a small cut through the chest wall and puts a thin, lighted tube called a thoracoscope into the chest between two ribs. Thoracoscopy allows the doctor to look inside the chest and obtain tissue samples.
If the cancer is in the abdomen, the doctor may perform a laparoscopy. To obtain tissue for examination, the doctor makes a small incision in the abdomen and inserts a special instrument into the abdominal cavity. If these procedures do not yield enough tissue, more extensive diagnostic surgery may be necessary.
To diagnose mesothelioma, the doctor will learn the stage (or extent) of the disease. Staging involves more tests in a careful attempt to find out whether the cancer has spread and, if so, to which parts of the body. Knowing the stage of the disease helps the doctor plan treatment.
There are three types of mesothelioma. Pleural mesothelioma is a cancer of the lining of the lung (pleura), peritoneal mesothelomia is a cancer of the lining of the abdominal cavity (peritoneum), and pericardial mesothelomia is a cancer of the lining surrounding the heart (pericardium). Sub-types (or cell types) of mesothelioma are epithelioid (the most common, and considered the most amenable to treatment), sarcomatous (a much more aggressive form), and biphasic or mixed (a combination of both of the other cell types).
The structural appearance of cells under the microscope determine the cell or sub-type of mesothelomia. Epithelioid is the least aggressive; sarcomatoid, the most aggressive. The biphasic or mixed cell type shows structural elements of both of the other two. More on the histologic subtypes of mesothelomia.
