Kai Y, et al. - In this analysis, the applicability of mucin 21 (MUC21), as a novel, negative diagnostic marker for epithelioid mesothelioma was immunohistochemically studied to differentiate mesothelioma from lung adenocarcinoma. For the expression of MUC21, along with other previously reported markers, by immunohistochemistry, 70 epithelioid mesothelioma and 70 lung adenocarcinoma cases were examined. To differentiate mesothelioma from lung adenocarcinoma, the researchers found that MUC21 could be used as an additional, novel, negative immunohistochemical marker.