Cellular changes in the basaloid cell papilloma.

Electron microscopic analyses of basaloid cell papillomas of the solid and papillomatous types are reported. The submicroscopic organization is described. Some of the ultrastructural findings, e.g. an increased number of mitochondria, a certain mitochondrial polymorphismus, the occurrence of irregularly shaped intracytoplasmic vesicles, the abundance of endoplasmic reticulum hypertrophy and the remarkable presence of microtubule-like structures, an unusual finding in a material fixed at the temperature used, are indicating an altered metabolic activity. The alternating presence and absence of keratohyalin is found to be submicromorphologically related to the formation of A- respectively B-cells. This is compared with the formation of parakeratosis in psoriatic lesions without keratohyalin. A formation of orthokeratosis as seen by the light microscopical procedure seems possible without preceeding occurrence of keratohyalin.