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Surgery Today

, Volume 30, Issue 1, pp 43–48 | Cite as

Evaluation of the Malignant Grade of Thymic Epithelial Tumors According to the Epithelial Subclassification

  • Satoshi Yoneda
  • Katsunobu Kawahara
  • Kan Okabayashi
  • Takeshi Shiraishi
  • Akinori Iwasaki
  • Takayuki Shirakusa
  • Junji Kohno
  • Masahiro Kikuchi

Abstract: We investigated the clinicopathological correlations among 49 surgically resected thymic epithelial tumors (TET), which were subclassified according to the six subtypes established by the Marino, Kirchner, and Müller-Hermelink system, which were renamed as follows: spindle cell type (medullary thymoma), mixed spindle and polygonal cell type (mixed medullary and cortical thymoma), small polygonal cell type (predominantly cortical thymoma), large polygonal cell type (cortical thymoma), atypical type (well differentiated thymic carcinoma), and cytologically malignant type (high-grade thymic carcinoma). The related categories were grouped for statistical analysis as follows: group 1, spindle cell type and mixed type; group 2, small polygonal cell type and large polygonal cell type; group 3, atypical type; group 4, cytologically malignant type. The association of each group with the presence of myasthenia gravis, tumor stage, and the length of survival was studied. Myasthenia gravis was significantly present in patients with small polygonal type, large polygonal type, and atypical type tumors (groups 2 and 3) (P = 0.003). The tumors in group 1 showed the lowest tumor stage while those of group 4 had the most advanced tumor stage (P = 0.002). The patients in group 4 had the worst prognosis, followed by those in group 3, 2, and 1, in that order. The differences among these groups were statistically significant (P = 0.0003). From our results, we determined that TET can be separated into an extremely low-grade malignancy group (group 1), a low-grade malignancy group (group 2), an intermediate malignancy group (group 3), and a high-grade malignancy group (group 4).

Key Words: thymic epithelial tumor, thymoma, thymic carcinoma, malignant grade, clinicopathologic classification 

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Copyright information

© Springer-Verlag Tokyo 2000

Authors and Affiliations

  • Satoshi Yoneda
    • 1
  • Katsunobu Kawahara
    • 1
  • Kan Okabayashi
    • 1
  • Takeshi Shiraishi
    • 1
  • Akinori Iwasaki
    • 1
  • Takayuki Shirakusa
    • 1
  • Junji Kohno
    • 3
  • Masahiro Kikuchi
    • 2
  1. 1. Second Department of Surgery, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-80, JapanJP
  2. 2. First Department of Pathology, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-80, JapanJP
  3. 3. Department of Pulmonary Surgery, National Sanatrium, Fukuoka Higashi Hospital, Fukuoka, JapanJP

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