Proliferating trichilemmal tumor-like neoplasm in the external auditory canal: A case report

Abstract Proliferating trichilemmal tumor (PTT) is a rare adnexal neoplasm of the hair follicle, which is usually detected on the scalp. We herein present a case of a PTT-like neoplasm arising in the external auditory canal (EAC). A man in his early sixties visited our hospital with a chief complaint of prolonged otorrhea. He underwent tympanoplasty on the basis of EAC cholesteatoma diagnosed at a local hospital, but otorrhea and debris recurred after the operation. Sixteen months after the first operation he was referred to our hospital. His EAC was filled with white debris, and computed tomography showed increased soft tissue density in the EAC and the middle ear. We performed a second operation, removing the entire circumference of EAC skin. Histopathological evaluation showed trichilemmal keratinization, which is characteristic of PTT. We concluded the patient had a PTT-like neoplasm. The tumor unfortunately became malignant fifteen months after the second operation. It is important to keep this clinical entity in mind when treating a patient with abnormal skin lesions in the EAC, as in this case presentation.