A study on epidermal proliferation ability in cholesteatoma.

With the objective of estimating proliferation ability of epidermis of middle ear cholesteatoma, the difference in proliferating cell nuclear antigen (PCNA) staining between the skin of the bone region of the external ear canal (control skin) and cholesteatoma epidermis and the effects on PCNA staining of subepidermal inflammatory cell infiltration of cholesteatoma were immunohistochemically studied using an antibody against PCNA. Transforming growth factor-alpha (TGF-alpha) is known to promote epidermal proliferation based on autocrine mechanism. But it is not clear that cholesteatoma epidermis is actually in the state of hyperproliferation under the effect of this growth factor. To estimate the effect of TGF-alpha on epidermal proliferation ability, the authors compared the location of PCNA and TGF-alpha in the same specimen. Unlike the control skin, not only epidermal basal cell layer and suprabasal cell layer, but also more superior layers were found to have high levels of PCNA staining in the epidermis of cholesteatoma. However, in the same cholesteatoma epidermal tissue, the PCNA staining was varied and the difference was ascribable to subepidermal cell inflammation. It appeared that the proliferation ability was high in regions where subepidermal inflammatory cell infiltration was severe. These differences in microenvironment are inferred to greatly affect proliferation ability of cholesteatoma epidermis.