Value of 18F-FDG PET/CT for Predicting the World Health Organization Malignant Grade of Thymic Epithelial Tumors: Focused in Volume-Dependent Parameters.PURPOSE
 We investigated whether preoperative parameters of 18F-FDG PET/CT were correlated with the World Health Organization (WHO) classification and/or Masaoka staging of thymic epithelial tumors.


 We reviewed 61 patients retrospectively who were diagnosed with thymic epithelial tumors after surgical resection and PET/CT. 
PET/CT
Value of 18F-FDG PET/CT for Predicting the World Health Organization Malignant Grade of Thymic Epithelial Tumors: Focused in Volume-Dependent Parameters.PURPOSE
 We investigated whether preoperative parameters of 18F-FDG PET/CT were correlated with the World Health Organization (WHO) classification and/or Masaoka staging of thymic epithelial tumors.


 We reviewed 61 patients retrospectively who were diagnosed with thymic epithelial tumors after surgical resection and PET/CT.  A volume of interest was drawn on the primary lesion, using an SUV cutoff of 2.5, and metabolic indices such as SUVmax, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured.


 The mean (SD) tumor size was 6.11 (3.41) cm.  There were 22 low-risk thymomas (36.9%) (A, AB, B1), 32 high-risk thymomas (51.6%), and 7 thymic carcinomas (11.5%).  Mean (SD) SUVmax was 3.43 (1.01) in low-risk thymomas, 4.42 (1.70) in high-risk thymomas, and 8.23 (2.61) in thymic carcinoma; the differences were significant (P < 0.001).  Mean (SD) MTV and TLG were 90.74 (114.56) and 229.36 (300.56) in low-risk thymomas, 80.82 (112.49) and 233.93 (340.91) in high-risk thymomas, and 90.63 (90.74) and 390.94 (437.62), respectively, in thymic carcinomas.  MTV and TLG showed no correlation with the WHO classification.  On receiver operating characteristic curve analysis, the cutoff value for discriminating thymomas and thymic carcinomas was 5.05.  SUVmax and TLG were correlated with Masaoka stage.


 CONCLUSIONS
 Although volume-dependent parameters were not correlated with the WHO classification, a significant relationship was observed between SUVmax and WHO classification and Masaoka stage.
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