Cytopathologic Diagnosis of Epithelioid and Mixed-Type Malignant Mesothelioma Ten Years of Clinical Experience in Relation to International Guidelines

Context.-Early diagnosis of malignant mesothelioma (MM) is urgently needed because life expectancies and treatment options are limited in advanced stages of the disease. Malignant mesothelioma often presents with recurrent hemorrhagic or inflammatory effusions, which might mask the incipient stages of the disease and thereby delay the diagnosis. Despite difficulties in recognizing the malignant cells present in those early effusions, they are often the first available biologic material for diagnosis. Therefore, awareness is needed, and efforts should be made to distinguish the malignant cells by well-defined morphological criteria, combined with ancillary methods. Objectives.-To summarize the diagnostic criteria for the cytopathologic diagnosis of MM based on recently published guidelines and to evaluate the clinical utility of those criteria in clinical practice. Data Sources.-The guidelines for the cytopathologic diagnosis of epithelioid and mixed-type MM and data in recent literature constitute the sources of this review. Eighty-five epithelioid or mixed-type MMs diagnosed between 2004 and 2013 at the Department of Clinical Pathology and Cytology, Karolinska University Hospital, Huddinge (Stockholm, Sweden), were evaluated to determine the clinical utility of the criteria defined by the guidelines. Conclusions.-A conclusive diagnosis of MM can be obtained based on the criteria defined by the guidelines with high positive predictive value. When diagnosed in this way, subsequent therapy should be initiated without further delay. With the earlier diagnosis obtained by cytology, a better effect of chemotherapy can be expected, as shown by the longer overall survival in these patients compared with those with a histopathologic diagnosis.