Value of immunohistochemistry in the differential diagnosis of pleural sarcomatoid mesothelioma from lung sarcomatoid carcinoma

The differential diagnosis of pleural sarcomatoid mesothelioma (SM) from lung sarcomatoid carcinoma (LSC) invading parietal pleura and chest wall is a challenging issue. The aim of this study was to identify useful antibodies that can be used for the differential diagnosis of pleural SM from LSC. Forty-five cases of pleural SM and 27 cases of LSC were immunohistochemically analysed by using 15 commercially available antibodies, including D2-40 and antibodies to calretinin, thrombomodulin, Wilms' Tumour 1, carcinoembryonic antigen (CEA), Napsin A, thyroid transcription factor (TTF)-1, pan-cytokeratin, CAM5.2, epithelial membrane antigen, Ber-EP4, MOC-31, alpha-smooth muscle actin, h-caldesmon and desmin. The results revealed that D2-40 positivity was significantly higher in pleural SM (86.7%) than in LSC (25.9%). The positivity of the adenocarcinoma markers, including CEA, Napsin A, and TTF-1, was low even in LSC. Evaluating the positivity and degree of staining of the well-known mesothelial marker D2-40 could be applied to differentiate pleural SM from the sarcomatoid component of LSC, in addition to assessing clinical and radiological information.