Epithelioid Lesions of the Serosa

Context.-Diagnosing epithelioid serosal lesions remains a challenge because numerous different processes-primary or secondary, benign or malignant-occur in body cavities, some of which are very rare. Objectives.-To review the newest literature and to describe the morphologic criteria and immunohistochemical markers that are useful for distinguishing epithelioid serosal lesions. Data Sources.-Previously published literature concentrating on the newest research findings. Earlier reviews are principally referred to for established diagnostic criteria. Conclusions.-Immunohistochemistry with a panel of antibodies has made the diagnosis of epithelioid serosal lesions very reliable. When deciding on antibodies used in differential diagnosis, it is important to consider tumor location, clinical and radiologic information, and morphologic features. Immunohistochemistry is less useful in the differential diagnosis of benign versus malignant mesothelial lesions. The diagnosis of benign versus malignant mesothelial proliferations still relies on the histologic criteria of invasion. (Arch Pathol Lab Med. 2012;136:241-252; doi:10.5858/arpa.2010-0216-RA)