[Scanning electron microscopy studies of the mucous membrane in precancerous conditions of the larynx].

In 21 cases of laryngeal cancer precursors (diffuse laryngitis chronica; so-called "plain", "verrucous" or "papillary" keratosis circumscripta) a microlaryngoscopy was performed, followed by microsurgical removal of the dysplasia. One part of each tissue specimen was studied histologically, the corresponding other part was observed in the SEM. In comparison of the microlaryngoscopic findings and histologic diagnoses on the one hand to the submicroscopic findings got by SEM on the other hand we may describe interesting characteristic structures of the laryngeal mucous membrane. Chronic laryngitis is represented in two different types: 1. plain parakeratotic type, 2. irregularly elevated hyperkeratotic type. Obviously last of them seems to have a greater tendency of malignant degeneration. The so-called "keratoses" represent specific SEM patterns according to their microlaryngoscopic pictures: - Homogeneous structure including sporadic parakeratotic keratinisation in cases of "plain" keratosis (mostly "leukoplakia"). - Irregularity of cell and tissue surface including cell walls, but also roughness and keratinisation of microvilli in cases of "verrucous" or "papillary" keratoses (mostly "pachydermia" or adult papilloma). - Characteristic SEM picture of cancer (echelon phenomenon) in cases of precancerous lesions, in which signs of atypia were proved histologically. Our SEM results confirm the value of an exact review of the laryngeal mucosa surface for laryngologists. Precancer diagnostics can be completed furthermore by intravital staining for instance. Nevertheless there is no doubt, that also a most careful surface diagnostics cannot replace histologic tissue examination in cases of early cancer detection. Obviously there are the limits of scanning electron microscopy in laryngeal cancer research.