Cytological Aspects of Atypical Squamous Metaplasia of the Bronchial Epithelium

Atypical squamous metaplasia of the bronchial epithelium was examined by cytological, histological, transmission and scanning electron microscopical techniques in 15 autopsy cases. To following three kinds of cells were found in the metaplastic area; 1) ciliated cells, 2) small metaplastic cells, 3) large metaplastic cells. While typical squamous metaplasia had a small number of small metaplastic cells, atypical metaplasia contained many. Furthermore, studies of cases of atypical squamous metaplasia revealed that highly atypical cells resembling adenocarcinoma were obtained by curettage. Ultrastructurally small metaplastic cells were similar to the small mucous granule cells described by McDowell and Trump. These findings suggest that atypical squamous metaplasia has a close relationship to highly atypical and adenocarcinomalike cells in sputum occasionally found in squamous metaplastic cells.