Pathological study of the malignant mesothelioma

Immunohistochemical staining for the carcinoembryonic antigen （CEA）, cytokeratin, vementin and histochemical staining for the periodic acid-schiff （PAS） with or without diastase digestion （DPAS） and the coloidal iron （GI） with or without hyaluronidase （HCI） treatment were performed in 31 malignant mesothelioma. Microvilli of the malignant mesothelioma（MM） and metastatic adenocarcinoma （AC） were examined by the use of electron microscopy. Positive staining for CEA was observed in 36 of 40 AC, but none in all 31 MM. MM cells showd a perinuclear or a peripheral distribution of positive staining for cytokeratin, while AC showed diffuse intracytoplasmic distribution. Positive staining for vimentin was observed in 17 of 24 MM, while it was negative in all AC. 29 of 31 MM were CI posititve, but negative for HCI. 32 of 40 AC were CI positive and also HGT positive. For MM microvillus, the average length to width was 11.76, versus 5.22 in the AC. The difference between the means was statistically markedly significant. These facts suggest that CEA, cytokeratin and vimentin may be valuable in the diagnosis of MM. The combined application of CI and HCI may be diagnostically useful in MM. The examination of microvilli with electron microscope may help distinguish MM from AC.