They considered a HEG1 membrane staining as positive and observed a diagnostic sensitivity and specificity of 91% and 99.7%, respectively, for PEM/PBM versus carcinomas from different sites (except for serous carcinoma of the ovary and thyroid carcinomas); at the same time, they further supported the diagnostic role of claudin-4, probably the best broad-spectrum carcinoma biomarker, showing a positive expression in about 1% of MPM. The gene discussed is CLDN4; the disease is carcinoma.