The Predictive Value Of MDCT For WHO Simplified Types And Masaoka-koga Stage In Thymic Epithelial Tumors

Objective:To analyze the MDCT features of thymic epithelial tumors and discuss the value of CT prediction for Masaoka-Koga stage and WHO simplified types,and the agreement between CT stage and Masaoka-Koga stage.Material and Methods:Collecting 105 thymic epithelial tumors patients with complete clinical and pathological data in the First Affiliated Hospital of Soochow University from January 2016 to June 2018.All patients had routine and enhanced thoracic CT scanning before surgery in 14 days.The CT characteristics of the 105 thymic epithelial tumors were reviewed retrospectively by two thoracic radiologists,without being informed WHO types and Masaoka-koga stage,and the final decisions on the findings were reached by consensus.According to the ITMIG definitions of thymic tumors,the location,size,contour(smooth,lobular,irregular),and presence of necrosis or cystic component and calcification,enhancement homogeneity(homogeneous,heterogeneous),enhancement degree(slight,moderate,obviously),the invasion of surrounding tissue(mediastinal adipose tissue,mediastinal pleural,pericardium,lungs,large vessels),pleural seeding,pulmonary metastasis and mediastinal lymph node enlargement were evaluated.Statistical analysis of image data above was performed by SPSS 22.0.All the categorical variables in the study were analyzed by using Fisher’s exact test.Differences in numeric variables using the analysis of t test.Results:According to the histological and immunohistochemical results,from WHO pathological classification perspective there were 7 patients of type A,21 of type AB,21 of type B1,23 of type B2,10 of type B3,and 23 of thymic carcinoma.Among the 105 thymic epithelial tumors patients,there were 57 of Masaoka-Koga stage 1,12 of stage II,27 of stage III,and 9 of stageIV.WHO simplified types was subcategorized as low-risk TETs(WHO classifications A,AB,and B1),high-risk TETs(B2 and B3),and thymic carcinoma.There was no significant difference in age,gender and general symptoms among different simplified types.21 patients were diagnosed with myasthenia gravis(MG),and it was more common in high-risk TETs,while rarely existed in patients of thymic carcinoma.There were no statistically differences in location of tumors,presence or absence of calcification between WHO simplified types.In our study,a greater average tumor diameter and irregular contour indicated thymic carcinomas.On the contrary,a shorter tumor diameter,smooth contour and uniform density often suggested low-risk TETs.There were no significant difference in enhanced images between WHO simplified types.The CT features of invading into surrounding tissue and metastases of TETs were more often seen in thymic carcinomas and high-risk TETs,and had statistically significant difference(P<0.05).Masaoka-Koga IV stage tumors were often had a larger diameter and irregular contour,rather,Masaoka-Koga I stage tumors had shorter diameter,smooth contour and uniform density disappearance.The CT features of invading into surrounding tissue and metastases of TETs had statistically differences in Masaoka-koga stage(P<0.05).Preoperative CT can be used for predicting tumor stage,especially for Masaoka-Koga III and IV stage.The weighted kappa coefficient between CT stage and Masaoka-Koga stage was 0.547.Conclusions:There were a certain overlap of MDCT findings between low risk and high risk TETs,high risk TETs and thymic carcinomas,but MDCT could distinguish low risk TETs from thymic carcinomas.MDCT could distinguish Masaoka-koga Ⅰ-Ⅱ stage from Ⅲ～Ⅳ stage TETs.Computed tomography stage showed moderate association with Masaoka-Koga stage(K=0.547).