A new World Health Organization (WHO) Classification of Tumors of the Pleura has recently been published. While the histologic classification of pleural malignant mesothelioma remains the same in the 2015 WHO classification as it was in the 2004 classification, multiple new observations have been recorded. First, more detailed study has been performed of histologic subtyping of epithelioid mesothelioma. In particular, it has been recognized that the pleomorphic subtype is associated with a poor prognosis, similar to that of sarcomatoid malignant mesothelioma.
