CD90 is a diagnostic marker to differentiate between malignant pleural mesothelioma and lung carcinoma with immunohistochemistry.

OBJECTIVES To pathologically distinguish mesothelioma from lung carcinoma, particularly adenocarcinoma. METHODS We conducted immunohistochemical analyses on clinical specimens, including 26 cases of mesothelioma, 28 cases of lung adenocarcinoma, and 33 cases of lung squamous cell carcinoma. RESULTS We found that CD90 expression was useful in making a differential diagnosis between epithelioid mesothelioma and lung adenocarcinoma, whereas sarcomatoid mesothelioma and lung carcinoma specimens, irrespective of the histologic types, were negative in general. The sensitivity and specificity of CD90 expression in epithelioid mesothelioma and lung adenocarcinoma were comparable to those of well-established markers used for the differential diagnosis. CONCLUSIONS These data collectively indicate that CD90 is a novel diagnostic marker that contributes to a diagnosis of epithelioid mesothelioma.