title: Thymoma in middle mediastinum that induced tracheal compression-Case report and literature review.
abstract: BACKGROUND
  A thymoma, an epithelial neoplasm of the thymus, mainly occurs in the anterior mediastinum, while few are seen in the middle mediastinum.
  
  
  METHODS
  An 83-year-old male was referred for an incidental mass in the middle mediastinum. He had severe dementia and denied symptoms. Our follow-up computed tomography (CT) examinations had revealed the progress of tracheal compression along with tumor enlargement for 2 years. At 85 years old, we performed a thymomectomy via a median sternotomy to avoid complete trachea obstruction. The pathological diagnosis was WHO type A thymoma, Masaoka stage II. One year after surgery, the patient was free of disease.
  
  
  CONCLUSIONS
  Thymomas occurring in the middle mediastinum are rare. In our review of 13 such cases, none were Masaoka stage III or IV, while the majority (9/13, 69.2%) were WHO type A or AB.
  
  
  CONCLUSIONS
  We encountered a thymoma in the middle mediastinum that showed enlargement over a 2-year period, inducing severe tracheal compression. Thymomas can occur widely in pharyngeal pouch-derived locations and should be considered in differential diagnosis of a middle mediastinum tumor.
authors.affiliation: Department of Thoracic Surgery, Kindai University Nara Hospital, Otoda-Cho 1248-1, Ikoma, Nara 630-0293, Japan. Electronic address: 2pinkyempress@gmail.com.
authors.forename: Teiko
authors.initials: T
authors.lastname: Sakurai
authors.affiliation: Department of Thoracic Surgery, Kindai University Nara Hospital, Otoda-Cho 1248-1, Ikoma, Nara 630-0293, Japan.
authors.forename: Tetsuki
authors.initials: T
authors.lastname: Sakamoto
authors.affiliation: Department of Diagnostic Pathology and Laboratory Medicine, Kindai University Nara Hospital, Otoda-Cho 1248-1, Ikoma, Nara 630-0293, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Wakasa
authors.affiliation: Department of Diagnostic Pathology and Laboratory Medicine, Kindai University Nara Hospital, Otoda-Cho 1248-1, Ikoma, Nara 630-0293, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Ohta
authors.affiliation: Department of Thoracic Surgery, Kindai University Nara Hospital, Otoda-Cho 1248-1, Ikoma, Nara 630-0293, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Shiono
keywords: Case report; Middle mediastinum tumor; Thymoma; Tracheal compression