title: Rare case of external dental fistula of the submental region misdiagnosed as inverted follicular keratosis and thyroglossal duct cyst.
abstract: BACKGROUND
  Odontogenic cutaneous sinus tract is a relatively rare occurrence that can be complicated to diagnose. The presence of a cutaneous lesion is often not even partly associated with a dental etiology because of the less frequency of occurrence in the case of dental symptoms. Consequently, the underlying dental cause is often missed leading to inappropriate diagnosis and treatment.
  
  
  METHODS
  Here, we report the case of a 45-year-old man who presented with a persistent lesion of the cervical region. At the time of presentation, the lesion had been present for approximately one year with a gradual increase in size but no specific symptoms. The patient had previously undergone punch resection under local anesthesia, which resulted in a histopathological diagnosis of inverted follicular keratosis. A diagnosis was made of an odontogenic cutaneous sinus tract secondary to chronic apical periodontitis of the left mandibular second molar.
  
  
  CONCLUSIONS
  Cutaneous sinus tract in the face and neck is most likely to develop intraorally. Root canal treatment or surgical extractions are the common treatment choices. A previously reported review of 137 cases found that 106 (77%) were treated by extraction and 27 (20%) were treated by surgical or conservative nonsurgical endodontic therapy.
  
  
  CONCLUSIONS
  Early diagnosis of cutaneous sinus tract using proper aid is responsible for shortening the treatment duration and avoiding unnecessary treatment.
authors.affiliation: Department of Oral-Maxillofacial Surgery, Dentistry and Orthodontics, The University of Tokyo Hospital, Japan.
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Oral-Maxillofacial Surgery, Dentistry and Orthodontics, The University of Tokyo Hospital, Japan. Electronic address: suenaga-tky@umin.ac.jp.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Suenaga
authors.affiliation: Department of Oral-Maxillofacial Surgery, Dentistry and Orthodontics, The University of Tokyo Hospital, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Igarashi
authors.affiliation: Department of Oral-Maxillofacial Surgery, Dentistry and Orthodontics, The University of Tokyo Hospital, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Hoshi
authors.affiliation: Department of Oral-Maxillofacial Surgery, Dentistry and Orthodontics, The University of Tokyo Hospital, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Takato
keywords: Cutaneous dental sinus tract; Dental etiology; Dental pulp necrosis; Inverted follicular keratosis; Misdiagnosis; Root canal treatment; Surgical extractions; Thyroglossal duct cyst