Sequential cytologic study of the development of squamous cell carcinoma induced in subcutaneously implanted bronchial autograft of dog

Squamous cell metaplasias and the development of squamous cell carcinomas caused by carcinogenic polycyclic hydrocarbon exposure of the lumen of grafted dog bronchi were followed by cytology, and were correlated to histologically and ultrastructurally observed changes seen in the biopsy specimens at the same time periods. Cytologic specimens showed a progression from mild atypia of squamous metaplastic cells, to moderate atypia, and to marked atypia before the development of invasive squamous cell carcinoma. Histology obtained by the biopsy specimens revealed findings corresponding to these cytologic changes. In the premalignant phase, squamous dysplasia and carcinoma in situ-like changes were also seen. Ultrastructural findings of the epithelium, such as widened intercellular space, increasing tonofilaments, enlarged nuclei with deep indentations, and prominent nucleoli with microsegregation were characteristic changes in the preneoplastic stages. It was concluded that this method of cytology, reflecting histologic and ultrastructural changes, is a useful experimental tool for the comparative study of premalignant lesions in the human bronchus and their early neoplastic stages.