Value of thrombomodulin immunostaining in the diagnosis of mesothelioma

Aims: Even with the benefit of immunohistochemistry and electron microscopy, the differential diagnosis between epithelial mesothelioma and pulmonary adenocarcinoma is often difficult. In most instances, the diagnosis of mesothelioma must be reached by the use of immunohistochemical markers that react with adenocarcinomas, but not with mesotheliomas. The purpose of this study is to determine the value of thrombo‐modulin (TM) as a positive marker for mesothelioma when distinguishing epithelial pleural mesothelioma from pulmonary adenocarcinoma. Methods and results: TM was expressed in 28 (80%) of 35 epithelial pleural mesotheliomas, but only five (10.9%) of 46 pulmonary adenocarcinomas had appreciable reactivity for this marker. Conclusion: It is concluded that TM can be useful in separating pulmonary adenocarcinoma from epithelial mesothelioma, but it should be used only in conjunction with other immunohistochemical markers that are currently employed in distinguishing between these two types of malignancies.