N-cadherin distinguishes pleural mesotheliomas from lung adenocarcinomas: a ThinPrep immunocytochemical study.

Cadherins are a family of cell-cell adhesion proteins. The homotypic binding of cadherins is critical for cell sorting and tissue formation during organogenesis. Different cadherin subtypes show lineage specific tissue expression, which has been exploited to differentiate histologically similar tumors of varying ontogeny. By applying immunohistochemistry to tissue sections, the authors have previously documented the utility of N-cadherin in distinguishing between pleural mesotheliomas and lung adenocarcinomas, based on the observation that N-cadherin is expressed in the former disease but not in the latter. Because the diagnosis of these diseases is frequently rendered on cytologic material rather than tissue biopsies, the authors wanted to assess the utility of N-cadherin immunocytochemistry in evaluating material prepared with ThinPrep. The authors examined the cytologic material from 12 patients for the expression of N-cadherin using immunocytochemistry. Four patients had mesotheliomas and eight had adenocarcinomas. ThinPrep slides of the patients' pleural fluid were prepared and stained with the monoclonal antibody 13A9, which is specific for N-cadherin. Of the 12 cases studied, all 4 cases of pleural mesothelioma expressed N-cadherin in a specific cell-cell membrane location, and all 8 cases of lung adenocarcinoma were negative for N-cadherin. These results show that the N-cadherin specific antibody 13A9 is a suitable marker in material prepared with ThinPrep for the differentiation of pleural mesotheliomas from lung adenocarcinomas. This antibody should be included in the diagnostic immunocytochemical panel for evaluation of these malignancies.