The diagnosis of malignant mesothelioma can pose several problems to the surgical pathologist first the morphological appearances of the tumour are known to be diverse with mimicry of a range of both reactive and neoplastic conditions. 1 cytological diagnosis the pathological confirmation of malignant mesothelioma is made mainly by examining two types of materials cytological material from pleural peritoneal or pericardial exudates and rarely from the scrotum or biopsy material from the pleura the peritoneum the pericardium or the tunica vaginalis. Mesothelioma is a global problem its incidence is rising in europe and it is a major health problem in the usa and other parts of the world largely related to the previous use of asbestos products diagnosis which rests on the pathology is very difficult because of its diverse appearances and the potential for other diseases to mimic it. The diagnosis of malignant mesothelioma can pose several problems to the surgical pathologist first the morphological appearances of the tumour are known to be diverse with mimicry of a range of