Squamous metaplasia of the middle ear epithelium.

This study deals with the expression of cytokeratins (Cks) in squamous cell metaplastic lesions in rat and human middle ear. In rats, squamous metaplastic lesions could be induced during chronic otitis media. The histological features of these lesions were similar to those observed in the human middle ear. Immunohistochemistry revealed that squamous cell metaplasia in both rat and human middle ear is characterised by a loss of simple epithelial cell related Cks and the appearance of Cks characteristic of stratified and cornifying epithelia. This indicates a true change in the differentiation of the middle ear epithelium. It is concluded that the Ck profile of the cholesteatoma matrix cannot be used as a variable to decide whether the origin of cholesteatomas is epidermal or metaplastic. This rat model is suitable for studying squamous cell metaplasia in relation to cholesteatoma genesis.