Immunohistochemical diagnosis of epithelioid mesothelioma: an update.

Several new immunohistochemical markers that can assist in the diagnosis of mesotheliomas have been recognized recently. This article reviews the current information available on these markers and also provides a practical approach to the immunohistochemical diagnosis of epithelioid mesotheliomas. Current literature concerning immunohistochemical markers for epithelioid mesotheliomas was collected and reviewed. Literature emphasizing immunohistochemical diagnosis of epithelioid mesotheliomas was selected. Data deemed helpful to the general surgical pathologist for the diagnosis of epithelioid mesothelioma were included in this review. Markers identified as potentially useful in the diagnosis of epithelioid mesothelioma include positive markers (namely, calretinin, keratin 5/6, D2-40, podoplanin, mesothelin, and Wilms tumor 1 protein [WT1]) and negative markers (namely, carcinoembryonic antigen, MOC-31, B72.3, and Ber-EP4). Thyroid transcription factor 1 (TTF-1) can assist in determining the lung origin of a carcinoma, and renal cell carcinoma marker (RCC Ma) may help establish its renal origin. D2-40 and podoplanin are the 2 most recently recognized markers that have been found to be useful in the diagnosis of epithelioid mesotheliomas. Since D2-40 and podoplanin appear to be highly sensitive and specific for epithelioid mesotheliomas, either may be considered for inclusion in the battery of antibodies currently recommended for distinguishing epithelioid mesotheliomas from metastatic carcinomas. However, it should be kept in mind that their utility has not yet been fully determined in routine diagnostic work.