MSLN and mesothelioma: Subjects with mesothelioma, in comparison to subjects with benign effusions, had significantly higher pleural fluid mesothelin (median 38 nM vs. 4.6 nM, p<0.001) (Figure 3d) and serum mesothelin levels (median, 2.0 nM vs. 1.0 nM, p<0.001) (Figure 4d).