Updates on the pathologic diagnosis and classification of mesothelioma

Mesothelioma is a rare malignant tumor of the serosal membranes that can be challenging to diagnose, especially on small biopsy specimens. There are updated guidelines on the diagnosis and classification of mesothelioma, which incorporate advancements in understanding mesothelioma biology published in the literature over recent years. This review will discuss marked developments and/or improvements that have been made, including: (1) to the histologic classifications of mesothelioma; (2) the use of such classifications and nuclear grading in prognosis; (3) the indispensability of ancillary studies in the diagnosis of mesothelioma; (4) the application of these pleural based classifications and diagnostic schemes in peritoneal mesothelioma; and (5) the potential for diagnosis of mesothelioma in situ.