S100A9 and cholesteatoma: Real-time PCR of PI3, SPRR1B, LCN2 (lipocalin 2), MMP1, MMP9, MMP10, MMP12, SPP1, GJB2, Bcl-xl (BCL2L1), cIAP2 (BIRC3), S100A7A (koebnerisin), S100A9, SERPINB3, CEACAM6, KRT6B and SERPINB4 revealed that the expression levels of these proteins were higher in cholesteatoma than in external canal skin.