[Epidermal growth factor in cholesteatoma--the second report: the localization in the horny layer]

The localization of epidermal growth factor (EGF) in human cholesteatoma tissue, normal ear drum and external auditory canal skin was examined immunohistochemically, using avidin-biotin peroxidase complex method. Bouin-fixed tissue was stained for investigation of horny layer in the epidermis, because fixation in Bouin's solution provides better preservation of the antigen. In the horny layer of cholesteatoma tissue, 19 out of 24 cases had EGF-positive immunoreactivity (79%). In 2 cases of normal external auditory canal skin, 4 cases of normal ear drum and a case of postauricular skin, no EGF-immunoreactivity was revealed in the horny layer. EGF was assayed in the debris of cholesteatoma and the horny layer of the normal bony external canal with dot blot immunoassay. EGF content of the debris was higher than that of the horny layer of normal skin. The result of the first report suggests the activity of cholesteatoma exists in the subcutaneous tissue (see the previous paper). In this report EGF content of cholesteatoma in the horny layer was found higher than that of normal external skin. This result demonstrates that EGF in the horny layer plays an important role in accelerating the growth and bony destruction in cholesteatoma. To summarize these two reports, the following conclusion was reached. In the epidermis EGF content is equal in cholesteatoma and normal skin. But in the subcutaneous tissue and the horny layer EGF content of cholesteatoma is higher than that of normal skin. EGF in situ may be strongly related to the growth and bony destruction of cholesteatoma.