The transformation of laryngeal leucoplakia to cancer.

In the transformation of laryngeal keratosis to cancer what one may be witnessing is a progression from normal epithelium to keratosis without cellular atypia, through varying degrees of atypia to the stage of carcinoma-in-situ when the full thickness of the epithelium is occupied by atypical cells until finally, with breaching of the basement membrane, an invasive carcinoma occurs (Fig. 12). Although this is, in theory, an attractive sequence, in practice it seems rare to detect an alteration in the epithelium from keratosis without atypia to keratosis with atypia and furthermore most of the carcinomas which developed were not in-situ but invasive. Therefore the significant pathway is probably a change from normal non-keratinizing stratified squamous epithelium via keratosis with atypia to invasive carcinoma (Fig. 13).