Mesothelioma Diagnosis

Mesothelioma's symptoms are not unique to it and because the disease is relatively rare, cases of Mesothelioma being misdiagnosed are not uncommon. To provide an accurate diagnosis, a review of the patient's medical history is an important first step in its diagnosis. This review would include the patient's history of asbestos exposure followed by a complete physical examination, x-rays of the chest or abdomen, and lung function tests A CT scan or MRI may also be done at this time. If any of these tests prove suspicious for Mesothelioma; a biopsy might be necessary to confirm the diagnosis. Finally, there would be a careful assessment of the clinical and radiological findings.

Imaging Techniques in Diagnosing and Assessing Mesothelioma

There are several imaging techniques which may be useful in diagnosing Mesothelioma. These imaging techniques are employed when Mesothelioma is suspected due to the presence of pleural effusion and a history of occupational or secondary asbestos exposure is revealed. While these imaging techniques are valuable in determining the possibility of Mesothelioma, definitive diagnosis would still need samples of the fluids or tissue biopsy.

The most commonly used imaging methods include:

X-ray 
 
A chest x-ray can be used if pleural effusion (fluid build-up) which is confined to either the right (60%) or left (40%) lung, is suspected. Occasionally, a mass may be seen in the X-ray. And sometimes, signs of prior non-cancerous asbestos disease, such as pleural plaques or pleural calcification, or scarring due to asbestosis exposure, may also be seen.

Computed Tomography (CT)

CT scans can also define pleural effusion, as well as pleural thickening, pleural calcification, thickening of interlobular fissures, or possible chest wall invasion. A CT scan, however, is not able to differentiate between changes associated with benign asbestos disease (pleural disease); nor can it differentiate between adenocarcinoma of the lung, which may have spread to the pleura, and Mesothelioma. CT scans may also be used in guiding fine needle aspiration of pleural masses when a tissue diagnosis is needed.

Magnetic Resonance Imaging (MRI)

MRI scans are most often used when determining the extent of tumor prior to an aggressive treatment. Because MRIs provide images in multiple planes, they are better able to identify tumors as opposed to normal structures. They are also more accurate than CT scans in assessing enlargement of the mediastinal lymph nodes (those lymph nodes which lie between the two lungs).MRIs are also more accurate in showing clear diaphragmatic surfaces. Being able to assess the enlargement of the lymph nodes and to see the diaphragmatic surfaces, play an important role in surgical candidacy.

Positron Emission Tomography (PET)

Increasingly, PET imaging is now becoming an important part of the diagnosis and evaluation of Mesothelioma. While PET scans are not always covered under insurance, they are now considered to be the most useful imaging technique in the diagnosis of tumor sites, and the most superior in determining the staging of Mesothelioma. PET, is a procedure that produces powerful images of the body's biological functions and is used to determine the extent of malignant disease. Unlike conventional imaging such as x-rays, CT scans, and MRIs, PET does not show the body's anatomy. Rather, it shows the chemical function or metabolism of an organ or tissue.

The patient receives an intravenous injection of FDG, a glucose analog labeled with radioactive fluorine, and is then asked to lie still for 45 minutes to an hour while the isotope distributes throughout the body, and is absorbed by the cells. Then, while lying on a scanning bed, the patient will be moved slowly through a scanner which detects the injected tracer. This scanner creates a three-dimensional image of areas of increased metabolism (cancers), which appear as "hot spots". When the imaging is complete, the results are sent to a computer where the images are reviewed by a physician. The patient's doctor will then receive a report and an image detailing the findings of the examination.

Most PET scans are completed in 2-4 hours. There are no adverse reactions to the scan, and there have been no reported allergies to the injection. The total radiation dose is less than that of a CT scan, or equal to about two chest x-rays. The majority of the radiation is eliminated from the body within 18 hours.

CT/PET

For patients who may be candidates for aggressive multimodality treatment (surgery, chemotherapy and radiation), accurate clinical staging is extremely important. Integrated CT/PET imaging has become the imaging technique of choice for determining surgical eligibility. By combining the benefits of CT and PET (anatomic and metabolic information) into a single scan, this technology can be used to more accurately determine the stage of the cancer, and can help identify the best treatment option for the patient.

Histopathological Examination

The only way to definitively diagnose and verify a suspected case of malignant Mesothelioma is through a biopsy.

A biopsy is a relatively minor procedure during which a small section of suspect tissue is removed. The removed section is examined by a histopathologist. The Histopathological examination can confirm a case of malignant Mesothelioma while also typing and staging it. Understanding the type and stage can help doctors make the best choice of treatment.