Simultaneous Immunoenzyme Staining of Vimentin and Cytokeratins with Monoclonal Antibodies As an Aid in the Differential Diagnosis of Malignant Mesothelioma from Pulmonary Adenocarcinoma

The occurrence and coexpression of the cytoskeletal proteins vimentin and cytokeratins were studied in malignant mesotheliomas and pulmonary carcinomas. For this purpose a double immunoenzyme staining with monoclonal antibodies was developed which made it possible to visualize vimentin and cytokeratins simultaneously within the same cell. A clear distinction between stromal cells (vimentin only) and tumour cells was also obtained. A total of 12 mesotheliomas (six mixed type and six epithelioid type) and 13 carcinomas (eight adenocarcinomas and five large cell undifferentiated carcinomas) were studied. The results revealed a clear difference between mesotheliomas and adenocarcinomas: 11 of 12 mesotheliomas showed coexpression of vimentin and cytokeratins in at least 50% of the tumour cells, while in seven of the eight adenocarcinomas none or only a few cells could be seen with this coexpression. In the undifferentiated large cell carcinomas three of five expressed both components, but in less than 25% of the cells. It is concluded that a reliable double immunoenzyme staining of vimentin and cytokeratins can be used as an additional means to distinguish malignant mesothelioma from pulmonary adenocarcinoma.