Cholesteatoma of the maxillary sinus.

Cholesteatoma of the maxillary sinus is a rare condition, but it should be considered in the differential diagnosis of any slowly expanding lesion of the maxillary sinus. Because the keratinizing squamous epithelium continues to desquamate and expand, thereby causing erosion of the surrounding structures, the cholesteatoma sac must be removed completely. We describe a case of cholesteatoma of the maxillary sinus in an 18-year-old woman.