Imaging Characteristics of Thymomas on Chest CT Classified by the 2004 WHO Classification

胸腺上皮瘤在電腦斷層上的表現：依據2004年WHO分類方法

林雁婷(Yen-Ting Lin) ； 蔡依橙(I-Chen Tsai) ； 陳啓昌(Clayton Chi-Chang Chen) ； 李覃(Tain Lee)

《中華放射線醫學雜誌》 33卷4期 (2008/12) Pp. 225-232

摘要

WHO對於胸腺上皮瘤的分類方式有助於預後的評估，依據2004年新版的分類法，我們回顧在2003年一月到2007年九月間，26個被診斷為胸腺上皮瘤的病人的病理組織分類以及在電腦斷層上的表現。
雖然在不同病理組織分類的胸腺上皮瘤的電腦斷層表現有彼此雷同的地方，但我們仍然觀察到type A的腫瘤表現出較多圓形且平滑的邊緣，而侵犯性較高的腫瘤以及胸腺癌則較多卵圓形、片狀型態並伴隨不規則的邊緣。此外，Type B3和胸腺癌有較高比率的腫瘤壞死。而縱膈腔侵犯以及遠端轉移較常見於胸腺癌。在我們的研究裡，腫瘤的鈣化僅出現於type B，並無例外。
總結來說，雖然不同病理型態的胸腺上皮瘤之影像表現有雷同的現象，但胸腺癌最常表現出不規則的邊緣、腫瘤壞死、縱膈腔侵犯、大血管侵犯以及遠端轉移。

並列摘要

The World Health Organization (WHO) histopathologic classification of thymic epithelial neoplasms has been considered to have prognostic value and can be directly correlated with clinical behavior. However, to the best of our knowledge, no studies have described the CT findings of thymic epithelial tumors by using the 2004 WHO classification.
To summarize the CT findings of different histological subtypes according to the 2004 WHO classification of thymic epithelial tumors.
Materials and Methods: We retrospectively reviewed all the histologically proven thymic epithelial tumors in our hospital from January 2003 to September 2007 according to the 2004 WHO classification. The initial chest CT scans and the image characteristics were reviewed. The CT findings for each histological subtype were also compared.
The CT images of 26 patients with thymic epithelial tumors were reviewed and there was some overlapping of CT findings among different histological subtypes. However, a high percentage of type A tumors were round shaped with smooth contours while more invasive thymomas and thymic carcinomas were more oval or plaque shaped with irregular contours. Type B3 thymic tumors and thymic carcinomas had a high percentage of tumor necrosis (75% and 78%, respectively) in comparison with type A and type AB tumors (25% and 25%, respectively). Calcifications were observed in type B group tumors without exception in our study. In addition, mediastinal involvement and metastasis were frequently seen in thymic carcinomas.
The CT features of different subtypes of thymomas tend to overlap. But irregular shape, presence of necrosis, mediastinal fat invasion, great vessel invasion, and metastasis are diagnostic features which suggest thymic carcinoma.