Pleural calcifications are common findings in most patients with a past history of exposure to asbestos. One in five of patients with asbestos exposure may have pleural plaques in the outer surface of the lung or within the lung tissue proper as seen by the CT scan. If mesothelioma is suspected in a person, the initial diagnostic evaluation may include CT scan or MRI of the chest. Mesothelioma may present as pleural thickening, pleural mass or pleural effusion. CT appearance of a pleural mass may be typical and a distinction between non-cancerous lesions and cancerous lesion can generally be made. But CT scan may not be able to distinguish between primary lesion that started in the pleura and a cancer that has originated elsewhere and spread to the pleura. If further CT scans shows the presence of other abnormalities then it may be possible to identify a source of primary lesion, from where the metastatic spread may have occurred.
MRI is usual tool for visualization of the diaphragm and may demonstrate the presence of diaphragmatic involvement by the mesothelioma. MRI is also a good technique for evaluating bones and spinal cord. Positron emission tomography (PET) scan and video assisted thoracoscopy are other techniques that may be useful in the staging work-up of a case of malignant mesothelioma. Gallium scan may be good tool and may prove useful when PET scan is not available. Routine brain scans, bone scans, liver scans or evaluation for extension into the serosa are not usually done except in cases where involvement of these sites are suspected based on symptoms or lab abnormalities.
Pathological diagnosis of malignant mesothelioma
Since malignant pleural mesothelioma is a disease with very poor prognosis, and may be involved with litigation, accurate pathological diagnosis and documentation are very important. Initial diagnostic evaluation of a person with suspected mesothelioma may involve biopsy of the pleura with examination of the pleural fluid and this may sometime yield a diagnosis. When pleural biopsy and pleural fluid examination fails to give a clear diagnosis, surgical intervention may be required to get a sample of the tumor. Needle biopsy, thoracoscopy, and surgery may be associated with risk of seeding the tumor into uninvolved surrounding tissue or the scar, but nevertheless these procedures are often required to make a diagnosis. Radiotherapy to the scar tissue may be undertaken to decrease the risk seeding at that site.
If at the time of diagnostic surgery, if the surgeon finds that the tumor is small and probably has not spread to the lymph nodes, he or she may combine the diagnostic procedure with a definitive therapeutic surgical procedure. A sample of the opposite side lung is usually obtained to do a count of asbestos fibers. If the CT scan suggests the presence of tumor inside the bronchial tree physician may perform a brochoscopy for direct visualization and or biopsy. Mediastinoscopy and biopsy are sometimes undertaken especially in patients who are candidates for curative surgery.