Malignant mesothelioma

Abstract

The incidence of pleural mesothelioma is rising in the Western world and is expected to peak by the year 2020 in the UK. The role of asbestos in causing this disease is discussed and pathogenetic mechanisms by which asbestos may cause mesothelioma are considered. The macroscopic and microscopic pathology of mesothelioma is discussed in detail; the World Health Organization classification into epithelial, fibrous (spindle cell or sarcomatous) and biphasic types is used; and the rarer variants are described. A section of this review is devoted to the use of immunohistochemistry in the diagnosis of mesothelioma. This is of value in the exclusion of carcinoma but has the drawback that at the moment there is no specific marker for malignant mesothelial proliferations. Pathologists still rely on positive cytokeratin markers and negativity in the antibodies used to identify carcinomas, such as carcinoembryonic antigen. The role of electron microscopy in the diagnosis of this tumour is discussed. It is a useful agent in differentiating well-and moderately well-differentiated epithelial mesotheliomas from pulmonary and other adenocarcinomas. Full consideration is given to differential diagnosis of mesotheliomas and entities such as pseudomesotheliomatous adenocarcinomas are described. Benign lesions which may mimic mesothelioma are also discussed in the differential diagnosis. In summary this is a difficult tumour for any histopathologist to diagnose. It is essential that this is kept continually in mind during the diagnosis of any intrathoracic tumour. A full knowledge of the clinical details, radiology, findings at thoracoscopy or thoracotomy as well as a full range of immunohistochemical and other stains, has to be employed to reach a correct diagnosis.