Fine morphology of the advancing front of cholesteatome--experimental and human.

The fine morphology of the advancing front of the cholesteatoma and the mucocutaneous juction of implanted skin in the feline bulla have been investigated. Inflammatory cell infiltration was frequently observed at the advancing front and the mucocutaneous junction. It is suggested that this frequent inflammation at this junction is due to the lack of a tight seal. In the advancing front, epidermal migrating cells appear to be lower spinous cells (or "suprabasalar" cells) rather than basal cells. It appears that the slender cell processes of the migrating cells make the initial attachment to the fibrin and/or basement membrane left behind by the degenerated epithelial cells as a result of inflammation and migrate along these structures, using them as a guide. Implanted skin in the cat's bulla failed to develop a pearl formation but frequently developed an epiboly, in which case the epidermis receded and was partly replaced by mucous membrane, and its stroma was heavily invaded by mucous epithelium, resembling tubular glands.