Intracellular keratins in normal and pathological bronchial mucosa. Immunocytochemical studies on biopsies and cell suspensions.

The distribution of intracellular keratins was investigated in normal bronchial epithelium and in several morphologically distinct forms of respiratory tract carcinomas. This study was performed with two different experimentally produced antisera against normal human stratum corneum keratin and against keratin protein of MW 67,000 dalton, using indirect immunofluorescence and immunoperoxidase methods on tissue sections and cell suspensions. In normal bronchial epithelium, the basal cells were strongly labelled by both antisera. The ciliated columnar cells appeared devoid of cytokeratins in tissue sections but were strongly labelled with both antisera in cell suspensions. The goblet cells remained negative in every case. In squamous metaplasia of the bronchus, all epithelial cells were unevenly stained with both antisera. Among tumours, only the squamous cell carcinomas were strongly labelled by both antisera. Primary lung adenocarcinoma appeared weakly positive, whereas metastatic lung carcinomas, undifferentiated lung carcinomas, oat cell tumours, carcinoid tumours were negative. The immunocytochemical determination of keratins appeared to be of value in the study of normal and abnormal epithelial differentiation, in the diagnosis of poorly differentiated carcinomas and in their distinction from metastatic tumours of the lung.