MMP2 and cholesteatoma: Zhu, Xie and Wang17 (2001), in a study called “Matrix metalloproteinase2,9 expression in middle ear cholesteatoma and cancer”, by means of immunehistochemical methods for MMP 2 and 9, used 36 cholesteatomas and 10 external ear skin fragments and 16 middle ear cancer fragments, observed a direct relation between cholesteatomas and MMP2 and MMP9, thus concluding that this disorder between metalloproteinases and their inhibitors was one of the reasons for bone resorption in middle ear cancer and cholesteatoma cases.