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Malignant mesothelioma is a highly invasive malignant tumor originating from the pleura. Malignant mesothelioma is the most common type of primary pleural tumors. The clinical manifestations are related to invasive behavior, which usually locally invades the pleural cavity and surrounding structures. Without treatment, the median survival time was 4-12 months.
Figure 1. Photomicrograph of epithelioid localized malignant mesothelioma.
The etiology and mechanism of the disease are still not very clear, which may be related to the following factors:
1. Long term exposure to asbestos
Almost all kinds of asbestos fibers are related to the pathogenesis of mesothelioma, but the risk of each fiber is not the same. The most dangerous is to contact crocidolite, and the least dangerous is to contact crocidolite. The incubation period from the first exposure to asbestos to the onset is generally 20-40 years. The incidence of mesothelioma is directly proportional to the time and severity of exposure to asbestos.
2. Other non-asbestos reasons
Exposure to natural mineral fibers, chronic pleural infection (tuberculous pleurisy) and recurrent pulmonary infection. There are also cases of pleural mesothelioma caused by exposure to radiation. The time from exposure to radiation to the discovery of pleural mesothelioma is 7-36 years, with an average of 16 years.
3. Simian disease 40sv40 (infection)
In patients without asbestos exposure history, 30% -50% may be related to SV40 infection. In the era of polio epidemic, millions of Americans may be infected with SV40 due to the vaccination of Salk vaccine. Recently, SV40 was isolated from patients with brain tumors and mesothelioma. Carbon and his colleagues isolated SV40 fragments from 60% of mesothelioma patients and successfully induced mesothelioma after intrathoracic injection of SV40 in rats.
1. Early stage of lesion
The naked eye can see many white or gray particles, nodules or thin plates on the normal or opaque visceral or parietal pleura. With the development of the tumor, these nodules fuse and grow with each other. The pleural surface becomes thicker and thicker, occupying the pleural cavity. The encapsulated lung shrinks its volume and collapses the chest wall on the affected side.
2. Late stage of lesion
The tumor nodule extends in all directions and forms a continuous sheet, which can involve the diaphragm, intercostal muscle, mediastinal structure, pericardium and contralateral pleura. Once the pericardium and mediastinum are involved, the patient may die of the excessive restriction of the tumor on the heart and lung. 50% of autopsy patients found hematogenous metastasis, but it is rarely mentioned that mesothelioma originated from mesothelial stem cells, which can differentiate into epithelial or mesenchymal cells. Therefore, it is common to find two kinds of cells in the same tumor at the same time.
Histologically, diffuse or malignant mesothelioma can be divided into three types: epithelial type, sarcomatous (stromal) type, and mixed type. The epithelium of epithelial tumor cells has a variety of different structures, such as papillary, tubular, tubular papillary, ribbon or sheet.The patients with malignant pleural mesothelioma were more male than female (2:1). Most patients are between 40 and 70 years old. The average age of patients abroad is 60 years old, while in China it is only 45.2 years old. The typical clinical manifestations of patients with malignant mesothelioma include chest pain, dyspnea, cough, weight loss, fatigue, occasionally accompanied by fever and night sweats. These symptoms can exist for months before diagnosis. Patients with malignant pleural mesothelioma may have increased abdominal circumference, abdominal pain or discomfort, constipation, nausea, and occasionally umbilical hernia. The most common clinical manifestation of malignant pericardial mesothelioma is sudden death, which is often found at autopsy. Other symptoms include dyspnea, fever, night sweats, congestive heart failure, restrictive pericarditis, pericardial effusion, pericardial tamponade and myocardial infarction. Mesothelioma of tunica vaginalis usually presents as unilateral testicular mass.
Patients with exudative pleural effusion, especially those with a history of asbestos exposure, should be considered for the diagnosis of malignant pleural stromal dermatoma. Chest CT can determine the diagnosis, and chest CT examination can determine whether the pleural calcification or bone structure is damaged. When the tumor invaded the diaphragm and chest wall, magnetic resonance imaging was better than CT. Although pleural effusion cell smear, pleural biopsy and pleural effusion cell block section can make the diagnosis of malignancy, it can not distinguish between pleural metastatic adenocarcinoma and malignant mesothelioma.
| Symptoms | Descriptions |
| Palliative treatment | The pleural effusion of patients with malignant pleural mesothelioma will appear again soon after aspiration. Chemical agents are injected into the pleural cavity, causing pleural adhesion. The pleural effusion of most patients is controlled. In this way, if the pleurodesis fails or in patients who plan to undergo diagnostic thoracotomy, pleurodesis should be considered. |
| Surgical treatment | At present, there are various surgical measures for the treatment of malignant pleural mesothelioma, the first is extended pleuropneumonectomy, that is, radical resection of the involved part of the chest wall, the whole lung, diaphragm, mediastinum and pericardium. |
| Chemotherapy | Anthracyclines are effective for malignant pleural mesothelioma, followed by cisplatin, mitomycin, cyclophosphamide, fluorouracil, methotrexate, vinblastine amide, etc. at present, anthracyclines are mainly used in comprehensive chemotherapy. Cisplatin plus methotrexate chemotherapy continued until the disease did not worsen. |
| Radiotherapy | External radiotherapy is very disappointed with malignant pleural mesothelioma, but extended external radiotherapy is effective, which can relieve chest pain and control pleural effusion in some cases, but has no effect on the disease itself. A few patients survived for more than 5 years, but almost all patients still died of recurrence or metastasis. |
The average survival time of asbestos workers with malignant pleural mesothelioma was only 11.4 months from the onset of symptoms to death, and most patients died within one year. In the next step, we should integrate various treatment measures more scientifically, and develop new technologies at the same time.
Reference
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