抄録
Osteoma of the external auditory canal is a relatively rare tumor; 19 cases have been reported up to 1989. We treated an 18-year-old male who had suffered from hearing impairment and otorrhea of the left ear for two years. A mass was found occluding the left external auditory canal, protruding from the tympanosquamous suture. The mass measured 10×5×7mm, and its surface was covered with squamous epithelium. Pathological examination revealed that the matrix of the tumor was composed of osseous tissue which contained fibrovascular channels surrounded by lamellae of bone. The diagnosis was osteoma of the external auditory canal. Before Graham described the histopathological differences between osteoma and exostosis, there was much confusion about these conditions. Although 66 cases of osteoma of the external auditory canal have been reported up to 1989, only 19 of them are thought to be real osteomas on the basis of their histopathological findings; the others are not certain. The tympanosquamous and tympanomastoid sutures close in the late embryological stage. When the closure of those sutures is incomplete, an osteoma may develop from the remaining epiphysis of the suture.
