Immunohistochemical studies on the expression of pulmonary surfactant apoproteins in human lung carcinomas using monoclonal antibodies.

To reevaluate the expression of pulmonary surfactant apoproteins in lung carcinomas, cancerous tissues from 47 cases were immunohistochemically examined by the avidin-biotin peroxidase complex method using monoclonal antibodies. These antibodies recognized apoproteins in type II pneumocytes in normal and in hyperplastic alveoli and nonciliated columnal cells (Clara cells) in terminal bronchioles of noncancerous tissues. Cancer cells positive for surfactant apoproteins were observed in 11 out of 33 adenocarcinomas, including 1 case of bronchioloalveolar carcinoma. Interestingly, two cases of adenocarcinomas with ultrastructural features of Clara cells, which had metastatic lesions, were positively stained both in the primary and the metastatic sites. Two out of 4 adenosquamous carcinomas showed positive reaction, which was exclusively localized in the cells with papillary structure. The present study indicates that the expression of surfactant apoproteins in cancer cells occurs ubiquitously in adenocarcinomas, which are considered to be derived from the terminal air way.