Mesothelioma Diagnosis

A diagnosis of  mesothelioma is usually prompted by the patient noticing the presence of certain symptoms. Diagnosis based on symptoms alone, however, can be difficult to achieve because the first symptoms of mesothelioma are similar to any number of common illnesses, and about half of patients display no early symptoms.

More than half of patients who develop pleural mesothelioma have pain in their lower back or chest. Shortness of breath is commonly reported, and a smaller percentage indicate difficulty in swallowing, fever, fatigue, coughing, sweating, and weight loss. Less commonly, patients report hoarseness, swelling in the face and arms, weakness in the muscles, loss of sensory feelings, and coughing up blood. The symptoms of peritoneal mesothelioma include stomach pain, nausea, weight loss, and vomiting. There are also often fluids or masses in the abdomen. Pericardial mesothelioma sufferers show symptoms such as chest pain, cough, palpitations, and dyspnea.

Asbestos Exposure Information In a mesothelioma diagnosis, a medical professional will first interview the patient complaining of these symptoms and compile a complete medical history. The interview will assess risk factors—especially past exposure to asbestos—for mesothelioma. In addition, the doctor will perform a physical exam to detect certain subtle, non-symptomatic signs of the disease. The most common sign is the presence of fluids in the chest cavity (for pleural mesothelioma), the abdominal cavity (for peritoneal mesothelioma), or the perdicardium (for pericardial mesothelioma).

If any of these signs are present, the doctor will request imaging studies, including x-rays, CT scans, PET scans, and MRI scans, to confirm the diagnosis as well as to locate the asbestos cancer and determine its size and spread. Since symptoms may be present but might not be discovered during the physical exam, imaging studies are often requested for any patient with risk factors.

A chest x-ray might indicate an irregular thickening in the pleura, deposits of calcium on the pleura, or fluid in the chest cavity. These indicators are strong signs that indicate asbestos exposure which led to the development of mesothelioma. Computed tomography, or CT, scans can often show the pleural thickening of malignant mesothelioma, and are critical in determining the extent of the cancer's spread in the body (also known as the "staging" of the disease). The first CT scans are often performed with the assistance of a radiocontrast agent, which the patient receives intravenously or is asked to drink. A second set of scans is then taken without the radiocontrast agent. Magnetic resonance imaging (MRI) scans, which are similar to CT scans, are often used to examine the diaphragm, brain, and spinal cord.

It is important to determine whether thickened pleural tissues are a sign of cancer, or merely scar tissue from other, non-cancerous trauma to the tissues. Only a biopsy can determine this. However, a PET scan, in which the patient is injected with radioactive glucose, can lead to increased suspicions of mesothelioma. Cancer cells use energy much more quickly than other cells in the body, and immediately take up the radioactive sugars, causing them to be easily spotted on the scanner. If scans reveal possible mesothelioma, a biopsy will be performed.

Needle Biopsy To make a final diagnosis of mesothelioma, a surgeon or medical oncologist will undertake a biopsy of the suspicious tissues. The surgeon removes the tissue, usually under local anesthesia, and the tissue is prepared and examined microscopically by a pathologist. There are any number of different ways to perform a biopsy, depending on the location of the affected tissues. For cancers located in the chest cavity, the doctor will perform a thoracoscopy, making a small cut in the chest wall and inserting a thin tube called a thoracoscope into the chest, using the gap between ribs as an easy accessway. This lets the doctor look directly into the chest and take tissue samples directly. For abdominal cancers, the doctor will likely perform a peritoneoscopy. In this surgery, the doctor opens a small cut in the abdomen and inserts a peritoneoscope into the cavity to conduct his or her examination.

If pleural mesothelioma is suspected, the physician may also conduct a bronchoscopy. For a bronchoscopy, a lighted, flexible tube is inserted into the patient's mouth, worked carefully through the trachea, and inserted into the bronchi to examine the airway for masses or tumors. The tube may also be used to remove small amounts of tissue for biopsy.

A mediastinoscopy may also be used, particularly if the oncologist wants to rule out mediastinal involvement cancer. In a mediastinoscopy, a lighted and flexible tube is inserted at the neck, underneath the sternum (your breastbone). The tube is worked into the chest, and the examiner looks at the lymph nodes and removes samples. Mesothelioma does not often spread to the lymph nodes, but lung cancer often does, and so tumors or masses in the nodes may indicate that the patient has lung cancer rather than mesothelioma.

If not enough tissue can be obtained through any of these procedures, more invasive surgery may be needed. A surgeon can open the entire chest cavity with a thoracotomy, or the abdominal cavity with a laparotomy, so that he or she may remove larger samples of the tumor, or, occasionally, the entire tumor if it appears that the mass can be entirely removed.

Even when an adequate tissue sample is obtained, mesothelioma is a difficult diagnosis to make on the basis of the fluid cells, or even with tissue samples. Mesothelioma bears a strong resemblance to other forms of cancer under the microscope. Pleural mesothelioma is known to mimic lung cancer, and mistaken diagnoses are relatively common. Peritoneal mesothelioma bears a strong resemblance to some ovarian cancers.

In order to distinguish mesothelioma from other cancers, doctors often deploy advanced chemical tests that use special techniques to recognize specific chemical markers that are unique to mesothelioma. Doctors can run a test called an immunohistochemistry to examine different proteins on cell surfaces, which can distinguish between lung cancer and mesothelioma. A newer technique known as DNA microarray analysis actually examines the genetic material of the cancer directly; mesotheliomas have very different genetic patterns than do other cancers.

Scanning Electron Microscope Sample One important tool in the diagnosis of mesothelioma is the electron microscope. More than 100 times as powerful as optical microscopes used in the diagnosis of most other forms of cancer, this unique tool makes it possible to visually see some of the shape markers that make mesothelioma distinct from other cancers.



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