EXPRESSION OF A CELL-CYCLE-ASSOCIATED NUCLEAR ANTIGEN (MIB1) IN CHOLESTEATOMA AND AUDITORY MEATAL SKIN

Middle ear cholesteatoma is often invasive with consequent bone destru ction. Inflammatory stimulation of the underlying connective tissue, a s well as an autocrine mechanism, may be responsible far the dysregula tion and abnormal proliferative features of the keratinocytes in chole steatoma. Comparative investigations were performed to assess the epit helial cell kinetics of cholesteatoma and normal auditory meatal skin. Monoclonal antibody MIB 1 immunostaining (which recognizes a nuclear antigen expressed by dividing cells) was applied using the alkaline ph osphatase antialkaline phosphatase immunolabeling method. Specimens of normal auditory meatal skin (n = 7) revealed an average MIB 1 score ( quotient of the MIB 1-positive cells and the total number of cells) of 7.6 +/- 2.2%. Cholesteatoma samples (n = 13) showed an average MIB 1 score of 17.4 +/- 8.9% and a heterogeneity of proliferating epithelial areas. Epithelial cones growing toward the underlying stroma exhibite d high mitotic activity. Statistically, the results of this study conf irm a highly significant increase in the proliferation rate of cholest eatoma keratinocytes, which had an MIB I score that was 2.3 times high er than the score for keratinocytes of normal external auditory meatal skin.