The cholesteatoma was known to composed of be keratinizing striated squamous cells on the histology. On the previous study, we had found the cholesteatoma consisted of nonkeratinizing straited squamous epithelium, keratinizing epithelium, and
transitioning zone on light microscope. We tried the electromictoscpoic exam to elucidate the pathogenesis of the cholesteatoma. As a result, the keratinizing equithelium had many keratohy-alinene granules, tonofilaments, obvious desmosomes like
as
the
skin, the nonkeratininzing epithelium had few keratohyailne granulse and tonofilaments, and many obvious desmosomes. The transitional zone was composed of a few of keratohyaline granules and tonofilaments, large granule in the certain region. The
incomplete basement membrane formation was found at the severe inflammatory and hyperproliferating zone, but completely organized basement membrane was toward the keratinizng epithelium, Fully matured keratinzing epithelium of cholesteatoma was
similar
to the epithelium of the skin, because the basement membrane was intact, and the basal cells did not contact the inflammatory cells and fibroblasts, and the epithelium of the cholesteatoma was not different from the epithelium of the skin,
ultramicroscopically. Based upon the observation, we though that the nonkeratinizing epithelium of the cholesteatoma was continually proliferating and differentiating toward the matured keratinizing epithelium.
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