Malignant mesothelioma

Malignant mesothelioma 

Causes

Malignant mesothelioma is the most common type of tumor of the pleura

In 20% of malignant mesothelioma , the tumor arise from the peritoneum

Exposure to asbestos is the only known risk factor it can be established in over 50%of patients geographic areas of increased incidence are frequently associated with industries using asbestos in the manufacturing process such as shipbuilding



The risk extends beyond the worker directly exposed to the asbestos family members exposed to the dust of the clothing or the work environment are also at risk

Other risk factors have been identified including exposure to fibers with similar physical properties to amphibole and exposure to radiation
Cigarette smoking does not appear to increase the risk of malignant mesothelioma
 Even though asbestos exposure and smoking synergistically increase the risk for lung cancer malignant mesothelioma have a male predominance of 2:1 and most common after the age of 40
Pathophysiology

The exact etiologic role of asbestos fibers has not been elucidated , however the physical characteristics of specific fibers referred to as serpentine or amphibole have been shown to be important the serpentine fibers are large and curly and are generally not able to travel beyond larger
airways however the narrow straight amphibole fibers in particular the crocidolite fibers may navigate distally into the pulmonary parenchyma and are most clearly associated with mesothelioma

The latency period between asbestos exposure and the development of mesothelioma is at least 20 years

 The tumor generally is multicentric with multiple pleural - based nodules coalescing to form sheets of tumor

 This process initially involves the parietal pleura generally with early spread to the visceral surface and with a variable degree of invasion of surrounding structures
CLINICAL PRESENTATION

  Most patient present with dyspnea and chest pain over 90%have a pleural effusion

 Thoracentesis is diagnostic in less than 10%of patients frequently a thoracoscopy or open pleural biopsy with special stains is required to differentiate mesothelioma from adenocarcinoma

 Once the diagnosis is confirmed cell types can be distinguished as epithelial ,sarcomatous and mixed

 Epithelial types are associated with a more favorable prognosis and in some patients long term survival may be seen with no treatment
 
Sarcomatous and mixed tumors share a more aggressive course
MANAGEMENT

 The treatment of malignant mesotheliomas it has been the subject of a number of recent clinical trials the vast majority with limited success a new staging system has been devised that has clearly shown prognostic value however while prognosis does depend on the stage of the disease the problem is that many patient with advanced local or distant disease beyond curative potential

  Treatment options 

Include supportive care using a combination of surgery chemotherapy and radiation therapy
 
Surgical options include

Palliative approaches such as pleurectomy or talc pleurodesis palliative approaches may lead to local control and a modest improvement in short term survival

More radical surgical approaches such as extrapleural pneumonectomy followed by adjuvant chemotherapy and radiation

Have an increased morbidity rate current approach to malignant mesothelioma is based on tumor stage and pulmonary performance status
 
For patient with early stage and good pulmonary function extrapleural pneumonectomy is recommended especially for multimodaliity therapy if available

For more advanced disease or if patient have less than optimal pulmonary function or performance status talc pleurodesis or supportive therapy is recommended

 Intrapleural therapy has been explored to improve the locoregional control of malignant mesothelioma

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