title: A case of atypical type A thymoma variant.
abstract: BACKGROUND
  An atypical type A thymoma variant was newly added to the WHO classification of type A thymoma family in 2015.
  
  
  METHODS
  A 72-year-old female was present a large round mass in the anterior mediastinum. The radiological examination led to a preoperative diagnosis of non-invasive thymoma. Tumor resection was undertaken via median sternotomy. Complete removal of the mediastinal tumor was achieved. Pathological examination revealed that the tumor cells were spindle- and oval-shaped with atypia. Immunohistochemical work-up revealed that the tumor was type A thymoma. On the basis of these findings, the tumor was finally diagnosed to be an atypical type A thymoma variant.
  
  
  CONCLUSIONS
  Preoperative diagnosis as atypical type A thymoma variant based on radiological examination is difficult. In case of atypical type A thymoma variant, a careful postoperative systemic follow-up should be done.
authors: Department of Thoracic Surgery, division of Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, 663-8501, Japan. kogekogemasaki@gmail.com.
authors: Masaki
authors: http://orcid.org/0000-0002-3247-6025
authors: M
authors: Hashimoto
authors: Department of Pathology, Kinki University of Medicine, Osakasayama, Japan.
authors: Shigeki
authors: S
authors: Shimizu
authors: Department of Thoracic Surgery, division of Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, 663-8501, Japan.
authors: Teruhisa
authors: T
authors: Takuwa
authors: Department of Pathology, Hyogo College of Medicine, Nishinomiya, Japan.
authors: Yoshitane
authors: Y
authors: Tsukamoto
authors: Department of Pathology, Hyogo College of Medicine, Nishinomiya, Japan.
authors: Tohru
authors: T
authors: Tsujimura
authors: Department of Thoracic Surgery, division of Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, 663-8501, Japan.
authors: Seiki
authors: S
authors: Hasegawa
keywords: Atypia; Median sternotomy; Thymoma