LAUSR

The distinction of malignant mesothelioma from non-small cell lung carcinoma (NSCLC) usually requires immunohistochemistry, but some broad spectrum carcinoma markers stain mesotheliomas and it remains unclear which broad spectrum markers are most valuable for separating these malignancies. Here we directly compared the sensitivity and specificity of three broad spectrum carcinoma markers, claudin-4, Ber-EP4 and MOC-31, for distinguishing NSCLC from mesothelioma. Immunohistochemistry was performed on tissue microarrays containing 68 epithelioid mesotheliomas, 31 sarcomatoid mesotheliomas and 147 non-small cell lung cancers (53 adenocarcinomas, 60 squamous cell carcinomas, 13 large cell carcinomas and 21 sarcomatoid carcinomas). For adeno, squamous cell, and large cell carcinoma, claudin-4 staining was present in 103/126 cases (82%), MOC-31 staining in 112/126 cases (89%), and Ber-EP4 staining in 113/126 cases (90%); these values were not statistically different. Claudin-4 stained 0/68 (0%) epithelioid mesotheliomas, MOC-31 stained 22/68 (32%) and Ber-EP4 stained 24/68 (35%); thus the specificities for NSCLC versus epithelioid mesothelioma were 100%, 68% and 65%, respectively. Staining of sarcomatoid carcinomas was present in 7/21 (33%) cases for claudin-4, 8/21 (38%) cases for MOC-31, and 5/21 (24%) cases for Ber-EP4. All three markers were negative in 12/21 (57%) sarcomatoid carcinomas. Sarcomatoid mesotheliomas did not stain with any of these markers. We conclude that claudin-4 has considerably greater specificity and comparable sensitivity to MOC-31 and Ber-EP4 for separating NSCLC from epithelioid malignant mesothelioma. The use of all three markers may be necessary for sarcomatoid neoplasms given their limited sensitivity.