Correlation Of CT Features Of Thymic Epithelial Tumor To Their WHO Histological Classification And Pathologic Staging

Objective: Thymic epithelial tumors (TET), including thymoma and thymic carcinoma are starting from the thymus epithelial tissue, there are a broad spectrum of biologic and morphologic features.This study is retrospective analysis of 65 cases of TET surgical records,pathologic examination records and multislice spiral CT(MSCT) fingdings, in oeder to explore the diagnosis value of CT to indentify the invasion of TET,and the correlations of histologic classification of TET to their CT findings.Materials and methods:1. 65 patients with TET between March 2005 and December 2002 confirmed by surgery and pathology were retrospectively reviewed. There were 38 men and 27 women;mean age,42 years;age range,3-75 years.IN these patients,9 cases were cough or sputum,19 cases were chest tightness or chest pain, 37 cases because of physical or complications discovered that a tumor,and 18 cases were myasthenia gravis. 54 cases of TET surgical resection in patients with pathological results obtained, 11 patients with pathologic results obtained by the puncture. The time interval between CT and thymectomy was 7 days to 1 month,median, 11 days.2. Whit SIMENSE Sensation 16 spiral CT machines and GE 64 spiral CT machines, scan range is from thoracic inlet to the diaphragm. SIMENSE CT machine specifications is 120 KV, 200 mA, Field of view(FOV) is 220～380 mm, matrix 512×512,thickness and interval of 5～10 mm;GE CT machine specifications is 120 KV,300 mA,FOV of 360～360mm, matrix 512×512, thickness and interval are 5mm.All patients underwent unenhanced examination,55 routine enhanced scan,the contrast agent Omnipaque 60～100 ml(300 mgI/ml), injection flow rate of 2.0～3.0 ml/s.The MPR and VR images were obtained by the workstation.Lung window, window width 1500～1700, window level -400～-500; mediastinal window, window width 300～350, window level 30～40.3. CT images were reviewed, which determined its invasive and Masaoka clinical staging, and then compared with surgical records and pathologic examination.ALL histopathologic specimens were reviewed and divided according to the latest WHO classification by an pathologist,including 6 types:types A,AB,B1,B2,B3 and thymic carcinoma,and then simplify that into three subgroups:low-rosk thymomas(types A,AB,and B1),high-risk thymomas(types b2 and B3),and thymic carcinomas.4. Using SPSS 13.0, count data using the rank sum test rank correlation. Measurement data usingχ~2 test,when n≥40 and T≥5,it would take PearsonChi-square P ; when n≥40 and 1≤T≤5,it would take Continuity Correction P;when n<40 or T=0,it would use fisher's exact test.The differences of the long- and short- axis diameters between three subgroups use LSD test. Test level isα=0.05.( n=total number of cases, T=the number of cases of a single grid)Results1.The CT fingdings of TET 22 cases were non-invasive thymomas, tumor margin showed smooth performance, clear mediastinal fat layer, of which 14 cases showed round shape, homogeneous density.On the post-contrast images,the lesion showed homogeneous enhance.In 34 cases of invasive thymoma,all CT scans demonstrated irregular invasion to adjacent organs,of which 21 cases showed lobulated shape, 14 patients had cystic necrosis, 12 cases with calcification, 30 patients with disappearing of mediastinal fat layer.9 cases were thymic carcinomas, of which 8 cases showed lobulated or irregular shape, the edge was not smooth lesions in 7 cases,8 cases of cystic necrosis within the lesion,6 cases of prompt pleural invasion,5 patients had mediastinal lymph node or distant metastasis,8 cases of heterogeneous enhancement.2.CT fingdings of invasive tumors comparing with their pathological results In 36 cases of invasive tumors,all CT scans demonstrated the soft tissue mass in anterior mediastinum,with encapsulated tumors in 24 patients.The main findings were pleura invasion in 14, pericardium invasion in 9,cardiovascular invasion in 9.A total of 96 lesions could be controlled,the result is 86 true positive,7 false positive,0 true negative,three falsenegative,and accuracy was 89.6% (86/96).3. MSCT staging comparing with their pathologic staging 54 cases of TET by MSCT to determine tumor staging and then compared with the pathological staging, MSCT diagnostic accuracy of four stagings were 83.3% (15/18), 76.5% (13/17), 90.9% (10/11) , 100.0% (8 / 8), the overall accuracy of 85.2% (46/54).4.The correlations of WHO histologic classification to their pathological staging In 54 cases confirmed by surgery and pathology TET,there are type A 4 cases,type AB 6 cases,type B1 12 cases,type B2 14 cases,type B3 12 cases,6 cases of thymic carcinoma.In Masaoka staging,Ⅰperiod of 18 cases,Ⅱperiod of 17 cases,Ⅲ11 cases,Ⅳperiod of 8 cases. WHO histological classification and Masaoka staging had a significant correlation (γs = 0.597, P = 0.000).5. The correlations of CT fingdings to their histologic classification The study found 25 low-risk thymomas,31 high-risk thymomas,9 thymic carcinomas.On CT imaging,smooth margin, homogeneous density,clear mediastinal fat layer, homogeneous enhancement were more commonly seen in low-risk thymomas(types A,AB,B1).And thymic carcinomas were more likely to have irregular shapes, necrosis or cystic lesions,mediastinal fat invasion,pleural invasion, cardiovascular invasion,lymph node enlargement or extrathymic metastasis,and heterogeneous enhancement.It's difficult for CT to identify high-risk thymomas and low-risk thymomas, high-risk thymomas and thymic carcinomas.ConclusionMSCT is of grate value for TET diagnosing and planning treatment;And CT is also of grate value for invasive tumors in making preoperative staging,displaying lesion's extent,planning surgical scheme,evaluating. WHO histological classification and Masaoka staging had a significant correlation,they can provide important information for judging the prognosis.On CT imaging,smooth margin, homogeneous density,clear mediastinal fat layer, homogeneous enhancement were more commonly seen in low-risk thymomas(types A,AB,B1).And thymic carcinomas were more likely to have irregular shapes, necrosis or cystic lesions,mediastinal fat invasion,pleural invasion, cardiovascular invasion,lymph node enlargement or extrathymic metastasis,and heterogeneous enhancement.It's difficult for CT to identify high-risk thymomas and low-risk thymomas,high-risk thymomas and thymic carcinomas.