The large mastoid antrum.
D000328:Adult; D002781:Cholesteatoma / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D004428:Ear Neoplasms / Q000000981:diagnostic imaging; D004432:Ear, Middle / Q000002:abnormalities*; D005260:Female; D006801:Humans; D008297:Male; D008416:Mastoid / Q000000981:diagnostic imaging*; D008875:Middle Aged; D011859:Radiography; D014054:Tomography