[Altered cytokeratin expression of the epidermoid formation in the tympanic cavity of human fetuses].

The epidermoid formation (EF) in the developing human fetal middle ear is believed to have relationship with congenital cholesteatoma. Sixteen EFs were included in this study, of which 15 were simple EFs and one was hyperplastic EF. Four cytokeratin antibodies PK, CK13, CK18, and CK19 were used in an ABC immunohistochemical technique to compare the expression of the cytokeratin in the EFs, middle ear mucosa and external acoustic meatus skin. The results showed that the simple EFs had the same staining pattern of middle ear mucosa for all four antibodies and were different from external acoustic meatus skin. It was suggested that the simple EFs do not have the properties of an epidermis. The hyperplastic EF had an altered cytokeratin expression comparing to that of the middle ear mucosa. The expression of CK19 disappeared in the structure while the normal middle ear mucosa nearby had a positive staining for this antibody. PK staining pattern, characterized by the more intensive in the surface layer of the EF, was similar to that of external acoustic meatus skin. It is suggested that hyperplastic EF may acquire certain properties of epidermis, and may develop into congenital cholesteatoma.