Caveolin-1 is a novel immunohistochemical marker to differentiate epithelioid mesothelioma from lung adenocarcinoma.

The incidence of mesothelioma is increasing in Europe, Japan and other developing countries. There is difficulty in the accurate diagnosis of mesothelioma and its differentiation from lung adenocarcinoma. Mesothelioma shows a complex immunohistochemical profile. Therefore, the use of a immunohistochemical panel that includes both positive and negative mesothelial markers has become a general rule for its accurate diagnosis. However, they are still not sufficient. The aim was to assess the diagnostic utility of caveolin-1 (Cav-1), which is expressed in endothelial cells, alveolar type I pneumocytes and mesothelial cells, as a novel positive marker of mesothelioma. An immunohistochemical study of 80 cases of epithelioid mesothelioma and 80 cases of lung adenocarcinoma was performed for the analysis of the expression of Cav-1 and other markers. Cav-1 expression with a membranous and/or cytoplasmic pattern was found in all of the epithelioid mesothelioma. Of these, 42 cases (52.5%) showed Cav-1 expression in >50% of tumour cells, 34 cases (42.5%) in 6-50% of tumour cells, and four cases (5.0%) in <5% of tumour cells. In contrast, only six cases (7.5%) of lung adenocarcinoma showed focal Cav-1 expression in the cytoplasm of the tumour cells. The sensitivity and specificity of Cav-1 expression for the differentiation of epithelioid mesothelioma from lung adenocarcinoma were 100 and 92.5%, respectively. This is comparable or even superior to that of currently available positive markers such as calretinin or D2-40. Cav-1 is a novel immunohistochemical marker for the differentiation of epithelioid mesothelioma from lung adenocarcinoma.