Pleural mesothelioma (Malignant pleural endothelioma, Pleural carcinosarcoma, Pleural carcinoma)

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Pleural mesothelioma is a primary malignant tumor arising from the mesothelial cells of the parietal and visceral pleura. Symptoms of mesothelioma of the pleura are pain in the chest, shortness of breath, dry excruciating cough, progressive cachexia, exudative pleurisy. Tumor lesions of the pleura are diagnosed according to radiography, computed tomography and MRI, diagnostic thoracoscopy, cytological analysis of pleural effusion. For the treatment of pleural mesothelioma, the entire arsenal of antitumor therapy methods is used – surgical, chemotherapeutic, radiation treatment, immunotherapy, photodynamic therapy.

 

General information

Malignant mesothelioma (endothelioma) of the pleura is a cancer of the serous membranes of the lungs. The most common mesothelioma of the peritoneum and pleura, although it is also possible to affect the pericardium, the membranes of the testicles, ovaries and fallopian tubes. The incidence of mesothelioma is closely related to industrial hazards, namely, contact with asbestos. In pulmonology, pleural mesothelioma is diagnosed 100-200 times less frequently than lung cancer; predominantly men over 50 years of age are ill (the incidence is 15-20 cases per 1 million population). Pleural mesothelioma is very aggressive, often detected already in the later stages, so the outcome of the disease is usually unfavorable – survival, as a rule, does not exceed 1-2 years after diagnosis.

 

Causes of pleural mesothelioma

In most cases (up to 70%), pleural mesothelioma, like mesothelioma of other localizations, is an asbestos-induced tumor. The development of the disease is mainly influenced by two factors: asbestos exposure and the size of asbestos fibers. Pleural mesothelioma usually develops in persons who have been in prolonged and close contact with asbestos-containing products (miners, people living in close proximity to asbestos mining sites, workers in manufacturing industries). In this case, several decades (20 to 50 years) usually pass from the moment of contact with the mineral to the development of pleural mesothelioma.

It is believed that fibers with a length of 5 to 20 microns and a diameter of less than 1 micron have the greatest carcinogenic activity. By inhalation, they easily penetrate into the respiratory tract, and from there through the lymphatic tract – into the lung tissue and subpleural space. In addition to pleural mesothelioma, these invisible particles can serve as the initiator of asbestos pneumoconiosis – asbestosis. Due to the fact that asbestos is widely used in various industries (in the production of roofing, refractory, insulating materials, brake linings), most patients are often unaware and therefore deny contact with asbestos. Although smoking alone does not affect the incidence of pleural mesothelioma, its combination with asbestos dust inhalation increases the risk of the disease.

Less rare and significant risk factors for the development of malignant pleural mesothelioma include contact with various chemicals (liquid paraffin, copper, beryllium, nickel, etc.), radiation therapy for other cancers, and genetic predisposition. Some researchers associate the incidence of mesothelioma and some other cancers (non-Hodgkin’s lymphomas, brain tumors) with the carriage of the monkey SV-40 virus. The polio vaccine used for immunization in 1955–1962 was contaminated with this virus. Thus, millions of people in Europe and North America turned out to be carriers of the dangerous highly oncogenic SV-40 virus.

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Mesothelioma grows from a single layer of squamous epithelium (mesothelium) of the pleura. Initially, it grows in the form of grains, nodules on the parietal or visceral pleura. In the future, mesothelioma can take the form of a dense knot (nodular form) or diffusely spread along the pleura, surrounding it like a shell (diffuse form). Serous-fibrinous or hemorrhagic exudate accumulates in large quantities in the pleural cavity. In the later stages, pleural mesothelioma infiltrates the lung, intercostal muscles, diaphragm, and pericardium; metastasizes to lymph nodes, contralateral pleura.

 

Classification of pleural mesothelioma

The staging classification of pleural mesothelioma is based on the criterion of the degree of tumor spread. On this basis, four stages of the tumor process are distinguished:

  • I – the prevalence of the tumor is limited to unilateral lesions of the parietal pleura.
  • II – the spread of the tumor to the visceral pleura, invasion of the parenchyma of the lung or muscle layer of the diaphragm on the side of the lesion is added.
  • III – soft tissues of the chest wall, lymph nodes and fatty tissue of the mediastinum, pericardium are involved in the tumor process.
  • IV – damage to the opposite pleural cavity, ribs, spine, pericardium and myocardium, peritoneum; distant metastases are found.

There are three histological types of pleural mesothelioma:

  1. epithelioid (50-70%)
  2. sarcomatous (7-20%)
  3. mixed (20–25%)

 

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Symptoms of mesothelioma of the pleura

From the onset of a tumor to the appearance of clinical signs, it can take from several months to 4-5 years. Most patients at the time of admission to the pulmonology department present non-specific complaints of weakness, subfebrile condition, sweating, and weight loss. The diffuse form of pleural mesothelioma sometimes manifests with high fever and severe intoxication.

The cough is usually dry, hacking, however, with sprouting of the lung, the appearance of bloody sputum may be noted. Often, the phenomena of hypertrophic osteoarthropathy develop: defiguration of the fingers, bone pain, arthralgia and swelling of the joints.

With the development of tumor pleurisy, shortness of breath, pain in the corresponding half of the chest join. The pain syndrome can be quite pronounced and painful; possible irradiation of pain in the shoulder, shoulder blade, neck, abdomen. Shortness of breath and pain do not disappear even after the evacuation of the pleural exudate. Pleural effusion usually accumulates rapidly and in large quantities; it may be serous or hemorrhagic in nature. With limited mesothelioma of the pleura, local pain can be determined in the projection of the tumor node. In advanced stages, associated with germination and compression of neighboring structures by a tumor conglomerate, dysphonia and dysphagia, tachycardia, superior vena cava syndrome are detected.

 

Diagnosis of mesothelioma of the pleura

Plain chest radiography can only tentatively indicate pleural mesothelioma by such signs as the presence of massive hydrothorax, thickening of the parietal pleura, a decrease in the volume of the chest cavity, and displacement of the mediastinal organs. Ultrasound of the pleural cavity allows you to determine the volume of exudate in the pleural cavity, and after its evacuation, assess the condition of the serous membrane of the lung.

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The final confirmation of the diagnosis and determination of the stage of pleural mesothelioma becomes possible after performing CT or MRI of the lungs. On tomograms, nodular thickening of the pleura and interlobar fissures, pleural effusion, germination of tumor masses in the chest wall, mediastinum, diaphragm, etc. are clearly visualized.

All cases of mesothelioma of the pleura, identified using radiation diagnostic methods, must be morphologically verified. The most accessible method for obtaining pleural contents for cytological analysis is thoracocentesis. If the test results are negative, a percutaneous biopsy of the parietal pleura is performed. However, the sensitivity of these methods averages only 50-60%. Therefore, the most reliable diagnostically are thoracoscopic or open biopsy. Diagnostic thoracoscopy not only provides visual control during material sampling, but also allows you to clarify the stage of the tumor process, assess the operability of the tumor, and also perform pleurodesis.

 

Treatment of pleural mesothelioma

With respect to pleural mesothelioma, almost all currently existing methods of antitumor treatment are used, but their effectiveness remains low. With the rapid accumulation of pleural effusion, unloading punctures (pleurocentesis), constant drainage of the pleural cavity with a microcatheter are performed.

With a local form of pleural mesothelioma, it is possible to use surgical tactics. The most radical is the performance of extrapleural pleuropneumoectomy, which is often supplemented by the removal of the lymph nodes of the lung and mediastinum, resection of the diaphragm and pericardium with their subsequent plasty. Mortality after such extensive operations is high – up to 25-30%. Palliative methods of surgical treatment for malignant lesions of the pleura are pleurectomy, talcum pleurodesis, pleuro-peritoneal shunting. Typically, such methods are used by thoracic surgeons for therapy-refractory pleurisy as a preparation for further therapy.

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In most cases, pleural mesothelioma is treated with polychemotherapy (cisplatin + pemetrexed, cisplatin + gemcitabine, etc.). Perhaps intrapleural administration of chemotherapy drugs. Radiation therapy is usually not used as a method of self-treatment of pleural mesothelioma, but is used after the surgical stage, intraoperatively or symptomatically (to reduce pain). The combination of pleuropneumectomy with postoperative chemotherapy or radiation in some cases can increase survival up to several years. Other methods of treatment (photodynamic therapy, immunochemotherapy) also have no independent value.

 

Prognosis in mesothelioma

Pleural mesothelioma is one of the malignant tumors with a poor prognosis. Without treatment, the life expectancy of patients with pleural mesothelioma is about 6-8 months. However, the effectiveness of the treatment of this disease today is also not very high – the median survival is 13-15 months. The most promising is combined treatment (radical pleuropneumonectomy with adjuvant chemotherapy or radiation therapy) – in this case, life expectancy increases to 4 years or more. It is possible to prevent the development of pleural mesothelioma by eliminating contact with asbestos materials at work and at home.

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