Diagnosis of Mesothelioma

A biopsy is needed to confirm a diagnosis of mesothelioma. In a biopsy, a surgeon or a medical oncologist (a doctor who specializes in diagnosing and treating cancer) 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 peritoneoscopy. To obtain tissue for examination, the doctor makes a small opening in the abdomen and inserts a special instrument called a peritoneoscope into the abdominal cavity. If these procedures do not yield enough tissue, more extensive diagnostic surgery may be necessary.

If the diagnosis is mesothelioma, the doctor will want to 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.

Mesothelioma is described as localized if the cancer is found only on the membrane surface where it originated. It is classified as advanced if it has spread beyond the original membrane surface to other parts of the body, such as the lymph nodes, lungs, chest wall, or abdominal organs.

A doctor should be seen if a person experiences shortness of breath, chest pain, or pain or swelling in the abdomen. If these symptoms are present, the doctor may order an x ray of the abdomen or chest. The doctor will do a complete physical examination and take a thorough medical history. Then, one or more of the following methods may be used to ascertain whether mesothelioma is present.

• Imaging tests. These tests may include x rays, computed tomography (CT scans), or magnetic resonance imaging (MRI) to allow the doctor to visualize the area in question. These studies will help determine the location, size, and extent of the cancer.
• Pleural biopsy . Diagnosing mesothelioma requires an adequate biopsy specimen. However, because mesothelioma usually arises from the lower part of the diaphragmatic and/or parietal pleura, obtaining enough tissue may be difficult. A simple, or closed, pleural biopsy involves the insertion of a needle into the chest cavity to obtain tissue from the pleural membrane for analysis. This technique is minimally invasive and normally requires only local anesthesia. This technique, however, may not provide adequate material for the necessary stains of the tissue to make a diagnosis of mesothelioma. Moreover, since the biopsy is not done under direct vision, the sample may not be exactly in the area of the tumor. If the diagnosis cannot be made with this relatively noninvasive technique, an adequate tissue sample usually can be obtained via an open pleural biopsy. In this approach, a surgeon makes an incision on the patient's side and goes into the pleural space. This method allows maximum exploration of the pleural membranes as well. However, the technique requires general anesthesia.
• Thoracoscopy . A thoracoscopy, which is a relatively new technique, allows the doctor to look directly into the chest (pleural) cavity at the tumor and during the same operation to also take a tissue sample for laboratory analysis. The thoracoscopy is performed by making a small incision into the chest and using a tiny video camera to inspect the region. The doctor can then use forceps to obtain a tissue biopsy. A laparoscopy , a similar operation, is used to obtain a biopsy of a peritoneal tumor.
• Bronchoscopy . A bronchoscopy, which examines the airways, or a mediastinoscopy , which looks at the lymph nodes in the chest, allows the doctor to look at the area using a lighted tube. Samples may be taken with a needle and sent to the lab to find out if cancer cells are present. However, bronchoscopy and mediastinoscopy are not that effective for diagnosing mesothelioma, as the disease is seldom found within the airways or the lymph nodes.
• Surgery. This lets the doctor obtain a larger tumor sample or, on occasion, the entire tumor.

Diagnosing mesothelioma is often difficult, even with tissue biopsies. Microscopically, mesothelioma is often difficult to distinguish from several other forms of cancer. For this reason, certain laboratory tests are performed to help correctly diagnose mesothelioma. Some of these tests involve using antibodies to distinguish lung cancer from mesothelioma. Sometimes the tissue samples must be viewed under an electron microscope in order to get the correct diagnosis.