PTGER4 and mesothelioma: Recently, Ordonez et al have recommend a panel of four markers for mesothelioma (two positive and two negative) from calretinin, cytokeratin5/6 or WT1 for the positive markers and CEA, MOC-31, B72.3, Ber-EP4 or BG-8 for negative markers.5 Electron microscopy can also help in distinction; adenocarcinomas have short and thick microvilli as compared to mesotheliomas, which have very long, thin microvilli.6