The purpose of the current study was to research the pathogenesis of bony destruction of cholesteatoma. We conducted a case report. The study was performed at Fukushima Medical University. The first case involved a 21 trisomy, whereas the second case was cancer of the hypopharynx. Both cases showed cholesteatoma. The following histopathologic findings in the temporal bones of cholesteatoma were obtained. Bony destruction in cholesteatoma was detected in the lesion of the rupture of the cholesteatoma sac. Epithelial debris of cholesteatoma was scattered throughout the rupture of the cholesteatoma sac. Rupture of the matrix was the result of a small abscess. Rupture of the cholesteatoma sac was believed to have been a pathway of either endogenous substances from the matrix and/or epithelial debris of cholesteatoma.