Expression of mesothelial markers in malignant mesotheliomas: an immunohistochemical evaluation of 173 cases.

OBJECTIVE To see the distribution of Calretinin, thrombomodulin, CK5/6 and HBME-1 markers in various subtypes of mesotheliomas and extend the published data on this topic. The positivity of adenocarcinoma specific markers (CEA and BerEP4) in malignant mesotheliomas have also been evaluated. METHODS Various markers in 173 cases of malignant mesotheliomas received over a period of 8 years were evaluated by immunohistochemistry. RESULTS In majority of malignant mesotheliomas i.e., epithelioid and biphasic types, the positive staining patterns complement the gold standard histologic diagnosis. However, in a small minority mainly sarcomatoid variant, heavy reliance cannot be placed on these markers. CEA and BerEP4 are useful negative markers of mesotheliomas, although occasionally these are positive in clear cut mesotheliomas. CONCLUSIONS Specificity of various markers in malignant mesotheliomas should be assessed according to histologic subtypes. The existing generation of markers is not reliable in diagnosis of sarcomatoid mesotheliomas. Fortunately this forms only a small group of mesothelial malignancy. In common epithelioid and biphasic variants calretinin, thrombomodulin, CK5/6, HBME-1 are sensitive positive markers whereas CEA and BerEP4 are negative markers of malignant mesotheliomas.