er of differentiation (20). Immunohistochemical investigation in our study disclosed non-uniform patterns of expression of CK 13 and CK 16 in middle ear cholesteatoma tissue. Variation in intensity of the positively stained areas between different cho- lesteatoma samples as well as between different areas in the same sample was probably related to the different proliferative capacity of cholesteatoma. No specific staining was detected in the retroauricular skin used as a control. The expression of non- epidermal cytokeratins in middle ear cholesteatoma tissue gives arguments against the probable skin origin of MECh keratinocytes. Protein separation and Coomassie blue staining revealed signif- icantly different protein profile between cholesteatoma and HaCaT cells. Precised Western-blotting analysis demonstrated compar- atively stronger expression of CK 13 and 16 in cholesteatoma keratinocytes with regard to HaCaT cell line. 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