The expression of epithelial markers (cytokeratins,
Filaggrin, BerEp4 and EMA),
collagen IV and Ki67 was studied immunohistochemically in
cholesteatoma and compared with that in epidermis of meatal skin, squamous epithelium of eardrum and simple epithelium of middle ear mucosa. MNF116 (
cytokeratin 10, 17, 18) stained the full layer of normal epithelium and all
cholesteatoma specimens. CK10 and
Filaggrin were expressed in the upper layer of epidermis but more diffusely in
cholesteatoma. BerEp4 was found in the basal layer of normal epithelium but was detected in most epithelial cells in
cholesteatoma matrix. Variability was observed in EMA and CK14 immunostaining.
Collagen IV was localized in the basement membrane of normal epithelium with a continuously staining pattern, an observation also made in the
cholesteatomas studied. However, in one of these small areas the basement membrane was not stained with
collagen IV. Ki67 was expressed in nuclei of the cells in the basal layer of normal epithelium but extended to epithelial cells in the upper layers of
cholesteatoma matrix. The results of the present study indicate that the expression pattern of epithelial markers in
cholesteatoma corresponds to that in normal epidermis. The increasing expression of BerEp4 and Ki67 confirms the hyperproliferative nature of
cholesteatoma. Whether or not the lack of expression of
collagen IV in one of the
cholesteatomas reflects a true degradation of the basement membrane needs further investigation in extended materials.