The respiratory epithelium. III. Histogenesis of epidermoid metaplasia and carcinoma in situ in the human.

The histogenesis of epidermoid metaplasia and carcinoma in situ was analyzed in human bronchial epithelium. The conclusion is that epidermoid metaplasia and carcinoma in situ can result from conversion of mucous cells. This implies the direct transformation of one type of fully differentiated cell to another. The study therefore emphasizes the differentiation potentialities of the mucous cells that can divide and undergo goblet cell hyperplasia and epidermoid metaplasia. Epidermoid metaplasia is a common reaction to injury in the bronchus. In our series of cases it was especially frequent in patients without neoplastic disease who had undergone intratracheal intubation or tracheostomy and who had been maintained on a respirator in the Shock Trauma Unit, University of Maryland. Future studies will be required to distinguish the difference, if any, between epidermoid metaplasia destined to become malignant carcinoma and that which is not. One difference noted in this study was the absence of overt cornification in epidermoid metaplasia in patients without neoplastic disease.