Malignant Mesothelioma

Malignant Mesothelioma Diagnosis

When there is reason to suspect you may have a mesothelioma, one or more cancer diagnostic methods will be used by your doctor.

Patient medical history and physical examination

First, a full medical history is taken to establish cancer risk factors and presence of any possible symptoms. The medical history interview includes questions to determine where you may have been exposed to asbestos.

Next, a complete physical exam is conducted with the intent of revealing signs of malignant mesothelioma cancer or any other health problems. New patients with pleural mesotheliomas (malignant mesotheliomas of the chest) often have pleural effusion (fluid in their chest cavity) that is caused by the cancer. Ascites (fluid in the abdominal cavity) appears in cases of peritoneal mesothelioma, and pericardial effusion (fluid in the pericardium) may be found in cases of pericardial mesothelioma which can also be detected during the physical exam.

Imaging tests

A chest x-ray may reveal irregular thickening of the pleura, pleural calcifications (mineral deposits), lowering of the lung fissures (spaces between the lobes of the lungs), or a build up of fluid in the pleural space. These findings may suggest there was asbestos exposure leading to the development of a malignant mesothelioma.

Medical imaging studies including x-rays, computed tomography (CT) scans, and magnetic resonance imaging (MRI) scans will help determine the location, size, and extent of the cancer. The electronic CT scan uses a rotating x-ray beam to create a series of images of the body from many angles. A medical computer combines these images to produce very detailed cross-sectional images for parts of the body. If it is needed to highlight details on the CT scan, the patient may be asked for permission to have a mostly harmless dye injected into the bloodstream. The MRI uses magnetic fields and not x-rays to create pictures of selected areas of the body. And as with a CT scan, the computer will generate a cross-sectional image.

Testing of Fluid and Tissue Samples

Lung Fluid Testing
When a patient has a pleural effusion, a small sample of this fluid can be extracted from the patient by inserting a needle into the chest cavity. Another similar technique can be used to take a sample of abdominal fluid and pericardial fluid. The patient's fluid sample is then tested in a lab to show its chemical make-up and analyzed under a microscope to determine the presence or absence of cancer cells.

A sample of tissue from a pleural or pericardial tumor can be taken using a relatively new sample technique called thoracoscopy. A thoracoscope (telescope-like instrument connected to a video camera) is inserted through a small incision into the chest. The doctor can then see the cancer tumor through the thoracoscope and can use special forceps to take a tissue biopsy. In much the same fashion a laparoscopy can be used to see and obtain a biopsy of a peritoneal tumor. In thd procedure a flexible tube attached to a video camera is inserted into the abdominal cavity via small frontal incisions. Fluid can also be collected during thoracoscopy or laparoscopy.

Surgery, either a thoracotomy (opening of the chest cavity) or a laparotomy (opening of the abdominal cavity), will allow a surgeon to remove a larger sample of tumor or in some cases to remove it entirely.

For those patients who might have pleural malignant mesothelioma, the doctor may also do a bronchoscopy. In this procedure a flexible lighted tube is inserted through the mouth, down the trachea, and into the bronchi to see if there are other masses in the airway. Any small samples of abnormal-appearing tissue can be removed for testing.

The cancer patient may also have a mediastinoscopy. During this procedure a lighted tube is inserted under the sternum (chest bone) at the level of the neck and then moved way down into the chest. In this way the surgeon is then able to view the lymph nodes in this region and take samples to check for malignant mesothelioma.

The lymph nodes are small collections of immune system cells that help the body fight infections and different types of cancers. Lung cancers frequently spread to lymph nodes, but the mesotheliomas rarely do this. An examination of the lymph nodes will allow the doctor to determine whether a lung cancer is still localized or if it has begun to spread. It can also help the doctor in distinguishing lung cancer from malignant mesothelioma.

Even with fluid samples from the area around the lungs, abdomen, or heart, it can often be difficult to diagnose malignant mesothelioma and it is even hard to diagnose malignant mesothelioma with tissue from biopsies. This is because mesothelioma cells are difficult to tell apart from several other types of cancer cells when viewed under the microscope. For example, pleural mesothelioma can resemble various types of lung cancer, and peritoneal mesothelioma can resemble various cancers of the ovaries. For this reason special laboratory cancer tests are often done to pinpoint mesothelioma amidst several other cancer possibilities.

These specal lab tests use techniques to identify certain chemicals known to be present in mesotheliomas and are known to be different than those present in cancer of the lung or ovary. An electron microscope may also be helpful in diagnosing mesothelioma. The scanning electron microscope has a magnification power 100 times greater than the normal light microscope which is generally used in cancer diagnosis. This allows detection of the small parts of the cancer cells that distinguish mesothelioma cancer from other types of cancer.

The big difficulty in distinguishing between malignant mesothelioma and other forms of cancer or benign, non-cancerous pleural inflammation is the primary problem posed during making the initial diagnosis. The most popular medical diagnostic tools presently remain the open pleural biopsy performed during thoracoscopy which allows for direct inspection of the inside of the chest, and provides much information on the involvement of the other organs and any spread of disease. The less successful diognostic procedures are CT guided pleural biopsy or blind pleural biopsy. Along with the gross appearance of the tumor, pathologists often rely on a panel of histochemical and immunohistochemical stains to diagnose or exclude malignant mesothelioma. Currently the chemicals linked to prognosis of malignant mesothelioma are under study, but have not been validated for the general use for this type of cancer..

Prognostic Factors

Because pleural mesothelioma has been better studied than peritoneal mesothelioma we know more about the factors that are associated with the prognosis for pleural mesothelioma. A younger age at diagnosis, performance status (functional status), and the absence of a weight loss are associated with a more favorable prognosis for the disease.

Mesotheliomas are usually of three different cell types (histological analysis): 1) epithelial cell type - which has the most favorable cancer prognosis; 2) fibrosarcomatous cell type - which carries the worst prognosis, and 3) mixed cell type - has an intermediate prognosis for the patient.