Developmental Mechanisms of Laryngeal Papilloma : Distribution and Characteristics of the Epithelium in the Larynx

Human papilloma virus (HPV) types 6 and 11 are thought to infect the basal cells of the squamous epithelium. These infections cause laryngeal papillomatosis and condyloma acuminatum in the uterine cervix, which manifest the same pathological phenotype. The site of predilection is the junction of the stratified squamous epithelium and simple columnar epithelium (SCJ), however, the morphological characteristics of the epithelial junction in the larynx differ from that in the uterine cervix. Therefore, these observations suggest that the developmental mechanism of underlying the onset of laryngeal papilloma differs from that of condyloma acuminatum. The newborn larynx, which is infected by HPV in case of juvenile-onset laryngeal papillomatosis, has no SCJ in the supraglottic regions. This suggests that HPV infects the laryngeal epithelium with or without SCJ. Moreover, the immaturity of the epithelia in the newborn larynx allows HPV to easily infect the tissue. In investigations of adult larynges, the basal cells of the squamous epithelium and stratified ciliated epithelium in the larynx express p63, an epithelial stem cell marker. Integrin-α6 is, the receptor for HPV, is positive in the stratified ciliated epithelium and lower half of the squamous epithelium. These findings indicate that HPV is able to infect the squamous epithelium and stratified ciliated epithelium and that both infection with HPV in epithelial stem cells and stratification of epithelial cell layer are necessary for the development of laryngeal papilloma.