Pleural mesothelioma
Diagnosis and assessment
2.1. Clinical signs
The most frequent clinical signs are:
dyspnea
lateralized chest pain
The clinical manifestations of mesothelioma are generally nonspecific and insidious and should not be used alone as diagnostic criteria, even in the event of previous exposure to asbestos (recommendation, grade 1A).
2.2. Complementary diagnostic examinations
The chest x-ray may show unilateral pleural effusion or pleural thickening. It should not be used alone to establish the diagnosis of mesothelioma (recommendation, grade 1A).
Thoracic computed tomography is inappropriate for establishing a definitive diagnosis of mesothelioma, but diffuse or nodular pleural thickening is highly suggestive of this pathology (recommendation, grade 1A). If possible, it should be done after the effusion has been evacuated.
Magnetic resonance imaging is not a relevant examination for the diagnosis of mesothelioma (grade 1B).
The value of 18-FEG PET in the positive diagnosis or characterization of pleural lesions has not been demonstrated.
There are currently no reliable serum markers.
A bronchial fibroscopy can be performed to look for an associated pathology (expert opinion).
2.3. Anatomo-pathological examination
The diagnosis of mesothelioma is based on the anatomo-pathological examination. This diagnosis can be difficult because the morphological spectrum of mesothelioma is very wide, a source of diagnostic difficulties in particular with metastases from carcinomas, primary or secondary sarcomas and more rarely pleural locations of benign tumors or inflammatory pathologies.
The macroscopic appearance of mesothelioma can be different throughout its natural course. Other malignant tumors can have a pseudo-mesotheliomatous appearance (thymomas, carcinomas, lymphomas, angiosarcomas, etc.).
The microscopic features of mesothelioma are well defined in the international classification (WHO 2004) of pleural tumors, dominated by the epithelioid MPM. However, this tumor has various appearances and may look like a benign pleural lesion or metastatic lesions, which is more common than mesothelioma in the general population. The most frequent pleural tumors are the secondary sites of bronchial and mammary cancers and their appearance can simulate a mesothelioma on standard slides. Benign pleural lesions and pleural reaction lesions are also a diagnostic problem and can appear at the same age as mesothelioma (pleural effusion due to heart failure, pneumonia, cirrhosis, etc.). These lesions are secondary and have the appearance of atypical mesothelial hyperplasia.
3. Anatomical pathology
3.1. Pleural puncture cytology
The first anatomo-pathological examination to be performed because pleural effusion is often the first clinical manifestation. In case of suspicion of mesothelioma, the number of punctures must be limited to the maximum in order to limit the risks of seeding on the routes.
It is not recommended to make the diagnosis of mesothelioma on cytology alone because there is a significant risk of diagnostic error (recommendation, grade 1B).
It is recommended to obtain histological confirmation if there is a cytological suspicion of mesothelioma (grade 1B).
Cytology alone can be used to confirm a relapse or metastatic course (recommendation, grade 1B).
3.2. Thoracoscopy
Exam of choice for the diagnosis of mesothelioma because it allows a complete visual examination of the pleural cavity and multiple biopsies and of good size. It allows a diagnosis of mesothelioma in more than 90% of cases (grade 1A).
It is recommended to perform a diagnostic thoracoscopy, except in the case of preoperative contraindications or anterior pleural symphysis.
A pleural symphysis can be performed at the same time in cases of abundant effusion except in cases of diagnostic doubt, a prospect of pleurectomy or intra-pleural treatment.
It is recommended to perform biopsies of macroscopically normal and pathological pleura (grade 1C): at least 6 centimeter samples of the parietal pleura. If the pleura shows diffuse thickening, a deep biopsy of the parietal and visceral pleura is indicated.
It is not recommended to make the diagnosis of mesothelioma on frozen tissue sections (extemporaneous examination) (grade 1B).
3.3. Blind pleural biopsies
The histological diagnosis of mesothelioma on blind pleural biopsy using Abrams or Castelain's needle can only be made if the biopsy material is representative, in sufficient quantity to allow immunohistochemical analysis and in a clinical, radiological context.
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