Immunohistochemical investigations on external auditory canal cholesteatomas.

Abstract

The aim of the study was to analyze the biological behavior of external auditory canal cholesteatoma (EACC). The expression and distribution of relevant markers such as transforming growth factor-alpha (TGF-alpha), epidermal growth factor-receptor (EGFR), and the proliferation marker MIB 1 were studied in comparison with normal auditory meatal skin. EACC are uncommon and knowledge concerning etiology and pathogenesis is limited. Whether this is a unique entity remains controversially discussed. Immunohistochemical methods were used to study the expression and distribution TGF-alpha, EGFR, and the proliferation marker MIB 1 on 15 tissues samples. Only the spontaneous form of EACC was included in this study. Positive immunoreactivity for the proliferation marker MIB 1 could be demonstrated in keratinocytes in the basal and suprabasal layers of the epithelium. The number of MIB 1-positive proliferating cells in cholesteatoma was significantly higher than in normal external auditory skin. Cholesteatoma epithelium also showed an enhanced expression of TGF-alpha and EGFR. Inflammatory infiltrate was observed in the perimatrix to various degrees. These results suggest that similar to the middle ear cholesteatoma, a chronic inflammatory process underlies the EACC, and the inflammatory stimuli may alter keratinocyte proliferation.