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Proteasome subunit β5t expression in cervical ectopic thymoma
  1. Utano Tomaru1,
  2. Yosuke Yamada2,
  3. Akihiro Ishizu3,
  4. Toru Kuroda4,
  5. Yoshihiro Matsuno2,
  6. Masanori Kasahara1
  1. 1Department of Pathology, Hokkaido University Graduate School of Medicine, Sapporo, Japan
  2. 2Department of Surgical Pathology, Hokkaido University Hospital, Sapporo, Japan
  3. 3Faculty of Health Sciences, Hokkaido University, Sapporo, Japan
  4. 4Tomakomai City Hospital, Tomakomai, Japan
  1. Correspondence to Dr Utano Tomaru, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan; tomaruu{at}

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Cervical ectopic thymoma is extremely rare, and, till date, <30 cases have been reported in the literature.1 Although typical cases of thymic neoplasms show distinctive morphology, they may pose diagnostic challenges when the specimen consists of only small tissue as often encountered in needle biopsy. Cervical ectopic thymoma is often misdiagnosed as thyroid or lymph node masses; specifically, predominantly lymphocytic thymoma can be misdiagnosed as Hashimoto's thyroiditis or malignant lymphoma and predominantly epithelial thymoma as carcinoma, particularly of thyroid origin.2 Therefore, the availability of thymus-specific immunohistochemical markers that can verify thymic epithelial origin would be of great help in getting a proper diagnosis.

β5t is a recently discovered proteasomal β subunit expressed exclusively in thymic cortical epithelial cells in both humans and mice.3 ,4 It is a component of specialized 20S proteasomes known …

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  • Funding This work was supported in part by Grants-in-Aid for Scientific Research from The Ministry of Education, Culture, Sports, Science and Technology of Japan.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval All experiments were approved by the Medical Ethics Committees of Hokkaido University Graduate School of Medicine and Hospital.

  • Provenance and peer review Not commissioned; externally peer reviewed.