<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A non-neoplastic keratinizing mass with stratified squamous epithelium, frequently occurring in the meninges, central nervous system, bones of the skull, and most commonly in the middle ear and mastoid region.</n0:def-definition><n0:def-source>MSH2003_2003_05_12</n0:def-source></n0:ComplexDefinition>