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. Here, MMP9 is linked to cholesteatoma.