[Immunohistochemical basement membrane analysis of cholesteatoma epithelium]

Cholesteatoma is a disease with an epithelial state of hyperproliferation based on a disturbed cell-matrix interaction. An analysis of the basement membrane, which can modulate epithelial proliferation, reveals a dysfunction of this layer between cholesteatoma and stroma. Cholesteatoma specimens were obtained from six patients undergoing middle ear surgery. Immunohistochemical staining was performed using antibodies against the major components of basement membranes such as laminin, heparan sulfate proteoglycan (HSPG), collagen IV and fibronectin. In cholesteatoma epithelium, we found a fragmented basement membrane with small amounts of laminin and HSPG showing only occasional positively stained fragments while collagen IV was almost completely absent. In contrast, fibronectin demonstrated an intensive staining especially in the stroma adjacent to the basement membrane. This staining pattern resembles the initial rearrangement of the epithelial basement membrane in human skin wounds and provides evidence for a lost contact inhibition on the provisional fibronectin-layer as a reason for the hyperproliferative nature of cholesteatoma lesions.