Pleural mesothelioma is a primary malignant tumor arising from mesothelial cells of the parietal and visceral pleural leaflets. Symptoms of pleural mesothelioma are chest pain, shortness of breath, dry painful cough, progressive cachexia, exudative pleurisy. Tumor lesion of the pleura is 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 methods of antitumor therapy is used – surgical, chemotherapeutic, radiation treatment, immunotherapy, photodynamic therapy.
C45.0 Pleural mesothelioma
Malignant mesothelioma (endothelioma) of the pleura is a cancer of the serous membranes of the lungs. The most common are mesotheliomas of the peritoneum and pleura, although it is also possible to damage the pericardium, testicular membranes, 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 often than lung cancer; mostly men over 50 years old are ill (the frequency of the disease is 15-20 cases per 1 million population). Pleural mesothelioma proceeds very aggressively, it is often detected already in the late 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, as well as mesotheliomas 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 people who have been in prolonged and close contact with asbestos-containing products (mine workers, people living in close proximity to asbestos mining sites, manufacturing workers). At the same time, from the moment of contact with the mineral to the development of pleural mesothelioma, it usually takes several decades (from 20 to 50 years).
It is believed that fibers with a length of 5 to 20 microns and a diameter of less than 1 microns have the greatest carcinogenic activity. By inhalation, they easily penetrate into the respiratory tract, and from there through the lymphatic pathways – into the lung tissue and subpleural space. In addition to pleural mesothelioma, these invisible particles can serve as the initiator of asbestos pneumoconiosis – asbestos. Due to the fact that asbestos is widely used in various industries (in the production of roofing, refractory, insulation materials, brake pads), most patients often do not realize and therefore deny contact with asbestos. Despite the fact that smoking by itself does not affect the incidence of pleural mesothelioma, its combination with inhalation of asbestos dust 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 oncological diseases, genetic predisposition. Some researchers associate the incidence of mesothelioma and some other oncological diseases (non-Hodgkin’s lymphomas, brain tumors) with the carrier of the monkey virus SV–40. The polio vaccine, which was used for immunization in 1955-1962, was infected 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.
Mesothelioma grows from a single-layer flat epithelium (mesothelium) of the pleura. Initially, it grows in the form of grains, nodules on the parietal or visceral pleura. In the future, the mesothelioma can take the form of a dense node (nodular form) or diffusely spread through 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, pericardium; metastasizes to lymph nodes, contralateral pleura.
The staging classification of pleural mesothelioma is based on the criterion of the degree of tumor spread. According to this feature, there are four stages of the tumor process:
- I – the prevalence of the tumor is limited by unilateral lesion of the parietal pleura.
- II – the spread of the tumor to the visceral pleura is added, invasion of the parenchyma of the lung or muscle layer of the diaphragm on the side of the lesion.
- III – the soft tissues of the chest wall, lymph nodes and fatty tissue of the mediastinum, pericardium are involved in the tumor process.
- IV – lesion of the opposite pleural cavity, ribs, spine, pericardium and myocardium, peritoneum; distant metastases are detected.
There are three histological types of pleural mesothelioma:
- epithelioid (50-70%)
- sarcomatous (7-20%)
- mixed (20-25%)
Symptoms of pleural mesothelioma
From the moment of the appearance of the tumor to the appearance of clinical signs, it can take from several months to 4-5 years. Most patients at the time of hospitalization in the department of pulmonology present nonspecific complaints of weakness, subfebrility, sweating, weight loss. The diffuse form of pleural mesothelioma sometimes manifests with high fever and severe intoxication.
Cough is usually dry, nasal, however, with the germination of the lung, the appearance of bloody sputum may be noted. Hypertrophic osteoarthropathy often develops: finger defiguration, bone pain, arthralgia and joint swelling.
With the development of tumor pleurisy, shortness of breath and pain in the corresponding half of the chest are added. 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 evacuation of pleural exudate. Pleural effusion usually accumulates rapidly and in large quantities; it can have a serous or hemorrhagic character. With limited pleural mesothelioma, local soreness can be determined in the projection of the tumor node. In the advanced stages associated with the germination and compression of the tumor conglomerate of neighboring structures, dysphonia and dysphagia, tachycardia, superior vena cava syndrome are detected.
An overview chest X-ray can only tentatively indicate pleural mesothelioma with signs such as the presence of a massive hydrothorax, thickening of the parietal pleura, a decrease in the volume of the thoracic cavity, displacement of the mediastinal organs. Ultrasound of the pleural cavity allows to determine the volume of exudate in the pleural cavity, and after its evacuation to assess the condition of the serous membrane of the lung.
The final confirmation of the diagnosis and determination of the stage of pleural mesothelioma becomes possible after performing CT or MRI of the lungs. The tomograms clearly visualize the nodular thickening of the pleura and interstitial slits, pleural effusion, the germination of tumor masses into the chest wall, mediastinum, diaphragm, etc.
All cases of pleural mesothelioma detected by radiation diagnostic methods should be morphologically verified. The most accessible method of obtaining pleural contents for cytological analysis is thoracocentesis. If the results of the study are negative, a percutaneous biopsy of the parietal pleura is performed. However, the sensitivity of these methods is on average only 50-60%. Therefore, thoracoscopic or open biopsy is the most reliable in diagnostic terms. Diagnostic thoracoscopy not only provides visual control during the sampling of the material, but also allows you to clarify the stage of the tumor process, assess the operability of the tumor, as well as to carry out pleurodesis.
Pleural mesothelioma treatment
With regard to pleural mesothelioma, almost all currently existing methods of antitumor treatment are used, but their effectiveness remains low. With a rapid accumulation of pleural effusion, discharge punctures (pleurocentesis), constant drainage of the pleural cavity with a microcatheter are performed.
With a local form of pleural mesothelioma, surgical tactics can be used. The most radical is the performance of extrapleural pleuropneumectomy, 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 plastic surgery. Mortality after such extensive operations is high – up to 25-30%. Palliative methods of surgical treatment for malignant lesions of the pleura are pleurectomy, talc pleurodesis, pleuro-peritoneal bypass surgery. Usually such methods are used by thoracic surgeons with refractory pleurisy as a preparation for further therapy.
In most cases, pleural mesothelioma is treated with polychemotherapy (cisplatin + pemetrexed, cisplatin + gemcitabine, etc.). Intrapleural administration of chemotherapy drugs is possible. 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 allows to achieve an increase in survival up to several years. Other methods of treatment (photodynamic therapy, immunochemotherapy) also have no independent significance.
Pleural mesothelioma is one of the malignant tumors with an unfavorable prognosis. Without treatment, the life expectancy of patients with pleural mesothelioma is about 6-8 months. At the same time, the effectiveness of treatment of this disease today is also not too high – the median survival rate 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 mesothelyma by eliminating contact with asbestos materials at work and at home.
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