Two cases of ectopic hamartomatous thymoma

Chen Zhao, Taketo Yamada, Shigeru Kuramochi, Kazuto Yamazaki, Makio Mukai, Kaori Kameyama, Jun Ichi Hata

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14 Citations (Scopus)


Ectopic hamartomatous thymoma (EHT) is a rare benign neoplasm. Since it was named by Rosai et al. in 1984, 24 cases have been reported. We herein report two cases of EHT, one of which presented with massive myoid cells, and review the literature related to EHT. Both of our cases displayed the typical features of EHT: (1) nests of epithelial cells, including solid, cystic, or glandular epithelial islands; (2) spindle cells dominating the microscopic picture; and (3) adipose cells which in-termingle haphazardly to impart a hamartomatous quality to the tumor. In this paper, we observed massive myoid cells and the transition from spindle epithelial cell to myoid cell in one of our cases. Immunohistochemical examinations showed that the main component of EHT, spindle cells, was positive for cytokeratin and epithelial membrane antigen (EMA). Intriguingly, the myoid cells simultaneously expressed cytokeratin, EMA, myoglobin, and creatine kinase-mm, suggesting that myoid cells may originate from epithelial cells and are an intermediate state between epithelial cells and muscular cells.

Original languageEnglish
Pages (from-to)643-647
Number of pages5
JournalVirchows Archiv
Issue number6
Publication statusPublished - 2000
Externally publishedYes


  • Ectopic hamartomatous thymoma
  • Immunohistochemistry
  • Myoid cell

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Molecular Biology
  • Cell Biology


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