AKA Malignant Mesothelioma
Oncology
InBrief
by Kruti Vora, MS-3
Edited by: Charles L. Fishman, MD
Mesothelioma is a cancer of the mesothelium, which includes the pleura, peritoneum, pericardium, and tunica vaginalis. The pleura is the most common site of disease, and this is usually due to exposure to asbestos fibers. This cancer is aggressive in nature, and prognosis post diagnosis is poor.
This is an uncommon cancer, with only 2,500 - 3,000 mesotheliomas diagnosed in the U.S. each year. 80% or more are related to asbestos exposure, with exposure occurring 10 - 40 years earlier.
There are 3 cell types- epithelial 50%, sarcomatous (spindle-shaped mesenchymal cells) 16%, and biphasic 34%. The epithelial cell type has a better prognosis.
Signs and Symptoms
Pleural involvement of mesothelioma often has a slow onset of nonspecific pulmonary symptoms, which usually occur several decades after initial exposure to asbestos. Patients may have chest pain, dyspnea, cough, night sweats, or vocal hoarseness. As the disease progresses, patients may have systemic symptoms such as fatigue, fever, weakness, and weight loss, and symptoms of metastasis to the bone, liver, CNS, or invasion of local structures such as the brachial plexus or superior vena cava (causing SVC syndrome).
Diagnostic Evaluation and Differential Diagnosis
A history of asbestos exposure indicates risk for mesothelioma, however it is important to note that patients exposed to asbestos are still at higher risk of developing a bronchogenic carcinoma than mesothelioma.
Initial evaluation will include a chest x-ray and chest CT scan to look for pleural thickening, plaques, or effusions, which are characteristic of mesothelioma. For definitive diagnosis, patients undergo a video-assisted thoracoscopic (VATS) biopsy or open thoracotomy. Bronchoscopy is also performed with endobronchial ultrasound biopsies to evaluate for lymph node involvement. The VATS biopsy method has a higher diagnostic yield than pleural fluid cytology evaluation or closed pleural biopsy.
The diagnostic biopsy in mesothelioma is associated with positive staining for calretinin, vimentin and cytokerotin.
The disease is staged based on extent of local progression, whether or not the tumor can be resected, regional lymph nodes involvement, and the presence of distant metastasis.
Treatment and Recommended Follow-Up
Surgery remains the mainstay of treatment for localized mesothelioma. In more advanced disease, surgery remains controversial. Some patients who are good surgical candidates may undergo procedures as limited as partial pleurectomy or as invasive as extrapleural pneumonectomy (removal of pleura, ipsilateral lung, pericardium, and diaphragm). It is unclear which of these procedures provides the optimal survival benefit. Post procedure, chemotherapy and radiotherapy are generally required. Patients who are not surgical candidates are offered palliative radiation and chemotherapy, and symptomatic treatment of pleural effusions via pleurodesis, catheters, or pleurectomy. Immunotherapy is being investigated as a potential new treatment for mesothelioma.
Unfortunately, despite advances in treatment of mesothelioma, prognosis is still poor with life expectancy of 22.2 months for stage 1 patients with surgery, and 14.9 months for stage 4 patients with surgery. Without treatment, pleural mesothelioma patients live an average of 6-9 months. Patients must have close follow-up during and after treatment to monitor for disease recurrence.
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