Clinicopathological Characteristics And DNA Methylation Analysis Of Thymoma And Thymic Carcinoma

Part?:Clinicopathologic characteristics and prognosis of patients with surgically resected thymic epithelial tumorsBackground:Thymic epithelial tumors(TETs)including thymic cancer and thymoma,is a rare neoplasm that arising from the thymic epithelial cells.It is characterized by low incidence,extremely variability in histological appearance,clinical behavior and prognosis of patients.Prospective studies are comparatively limited that might cause the limited understanding of the disease and therefore throw a great challenge for the clinical patient management and prognostic prediction.Objective:The purpose of present section was to retrospectively analysis of patients with thymic epithelial tumors that were treated at our hospital,so as to provide additional information about disease characteristics for clinical patient care.Material and Methods:Patients with thymic epithelial tumors who underwent surgical resection at Peking Union Medical College Hospital between 2007 and 2017 years were retrospectively reviewed.Clinical data on demographic and clinicopathologic features,treatments and clinical outcomes were extracted from the electronic medical records,including age,sex,concomitant diseases,tumor size,Masaoka stage and/or TNM stage,WHO histologic type,clinical characteristics,surgery and postoperative adjuvant therapy(chemotherapy,radiotherapy,chemoradiotherapy,targeted therapy and others)administrated.Survival analysis was performed by Kaplan-Meier method.COX proportional harzard model was established to identify potential factors that may associate with overall survival or progression free survival of patients with thymic cancer.Results:A total of 337 patients who underwent surgical resection for thymic epithelial tumors between March 2007 and September 2017 were identified.There were 229 patients with thymoma and 108 with thymic cancer.Among the 229 patients with thymoma,118 cases were male and 111 were female.The median age of patients was 50.0 years(ranged from 15 to 79 years).Ninety-seven patients had concomitant diseases,most commonly myasthenia gravis,occurring in 79 patients(34.5%).The most common histologic type was type AB thymoma,occurring in 73 patients,followed by type B2 thymoma in 56 patients,type B3 thymoma in 41 patients,type B1 thymoma in 31 patients,type A thymoma in 15 patients and atypical A thymoma in 8 patients.The other 5 patients had uncommon histologic types.Masaoka staging analysis showed 106 stage ?,100 stage ?,20 stage ? and 3 stage IV.Most(227)patients underwent complete surgical resection for thymoma,and 52 patients received further postoperative adjuvant therapy.Two patients died within postoperative 30 days.During the long term follow up of 179 thymoma patients,10 patients had recurrent or metastatic disease and 4 patients died.The estimated 10-year progression free survival and overall survival of thymoma patients were 95.2%? 96%,respectively.As for the 108 patients with surgically resected thymic cancer,there were 64 male patients and 44 female patients.The median age of patients was 52.0 years(ranged from 22 to 80 years).Squamous cell carcinoma was the most common,accounting for 93.5%(101)of thymic cancer patients.Nine patients had concomitant diseases and only 3 cases of myasthenia gravis were identified.Five patients were at Masaoka stage ?,1 were at stage ?,75 were at stage ? and 27 at stage ?.Of the 108 patients with thymic cancer,64 patients achieved R0 resection and 79 patients received postoperative adjuvant therapy.One patient died perioperatively.Seventy-nine patients were followed up for a long time period,23 cases had recurrent or metastatic disease and 15 cases died.Cox regression analysis showed incomplete surgical resection(vs R0,HR=4.867,95%CI:1.087-21.789,P=0.039)was the only factors that were significantly associated with overall survival of patients with thymic cancer.Meanwhile,female sex(vs male:HR=0.309,95%CI:0.118-0.804,P=0.016),older age(?52 years vs<52 years,HR=4.792,95%CI:1.694-13.554,P=0.003)and vascular nerve invasion(HR=2.893,95%CI:1.165-7.180,P=0.022)were independently associated with progression free survival of patients.Conclusion:The clinicopathologic characteristics and survival of 337 patients who underwent surgical resection for thymic epithelial tumors at our hospital during March 2007 to September 2017 were retrospectively analyzed.Patients with thymoma were more likely to have concomitant diseases and most commonly myasthenia gravis.Histologic analysis showed type AB as the most common one.Most patients were at early Masaoka stage(89.9%AT Masaoka stage I-II).The estimated 10-year overall survival was 96%for our resected thymoma patients,suggesting the inertia of its biological behavior.Meanwhile,patients with thymic cancer had few concomitant diseases.The primary histology was squamous cell carcinoma.The estimated 3-year overall survival and progression free survival were 84.4%and 68.9%.Cox regression analysis indicated incomplete surgical resection was significantly associated with overall susrival,while sex and age were associated with progression free survival of thymic cancer patients.Part ?:Distinguishing between B3 thymoma and thymic cancer by using immunohistochemical methodBackground:Thymic cancer is a rare and highly aggressive thymic neoplasm that often shows early lymph node metastasis.The type B3 thymoma is a peculiar group that is also known as the well differentiated thymic carcinoma.The tissue morphology and biological behavior of type B3 thymoma and thymic cancer were alike to some extent,which makes the clinical diagnosis a challenge issue.In view of high sensitivity and specificity,as well as the advantage of joint consideration of location,morphology and function,immunohistochemistry has been commonly used for clinical patient diagnosis,treatment and prognostic prediction.However,potential immunohistochemical markers for distinguishing between thymic cancer and type B3 thymoma have not been well-established up to now.Objective:Present study aimed to investigate the potential role of immunohistochemical staning in distinguishing between thymic cancer and type B3 thymoma,so as to potential biomarkers for clinical utilization.Material and Methods:Patients with resected thymic cancer or type B3 thymoma that had enough tissue samples for immunohistochemical analysis were included in this study.Immunohistochemistry was performed using the antibodies against Mucin 1(MUC1),glucose transporter 1(GLUT1),protease ?5t subunite(?5t),CD5 and CD117(C-kit).The stains were defined as positivity when>10%of tumor cells showed positive.Clinical data including age,gender,concomitant diseases,tumor size and Masaoka stage were obtained.Specificity and sensitivity of each biomarker were tested for their diagnostic value.Results:There were 15 thymoma patients and 20 thymic cancer patients.Protein expressions of MUCI,GLUT 1,CD117 and CD5 were identified predominately in patients with thymic cancer,and showed positive rates of 70.0%,95.0%,85.0%and 85.0%,respectively.Meanwhile,their positive rates in thymoma patients were 6.7%,0.0%,0.0%and 13.3%.However,?5t was positively stanined in all thymoma patients(100%)and only one patient with thymic cancer was positive for ?5t.The diagnostic analysis showed high sensitivity(95.0%)and specificity(100.0%)for diagnosis of thymic cancer,followed in turn by CD117,CD5 and Mucl.Meanwhile,P5t positivity showed high sensitivity and specificity of 100.0%and 95.0%for thymoma diagnosis.Combination of Glut1 and ?5t immunotypes showed high sensitivity(95.0%),specificity(100.0%)and accuracy(97.1%)for distinguishing between type B3 thymoma and thymic cancer.The Youden index was 0.95.Conclusion:The findings of our study indicated that immunohistochemical staning of GLUT1 exhibited high sensitivity and specificity for thymic cancer,while immunoreactivity of ?5t showed high sensitivity and specificity for thymoma.Combination of GLUT1 positivity and ?5t negativity showed high sensitivity and specificity for distinguishing between type B3 thymoma and thymic cancer.Part ?:Genome-wide DNA methylation profile of thymomas and potential epigenetic biomarkers for thymoma subtypesBackground:Thymic epithelial tumor is a heterogeneous disease of thymic epithelial cell origin.Two major types of thymoma:type A and type B,are identified according to their morphological features.Epigenetics has been reported to play a role in the oncogene activation and anti-oncogene inactivation that may contribute to the malignant transformation of cells and development and progression of cancer.Objective:Present study aimed to explore the whole methylation status of thymomas and to identify potential biomarkers for distinguishing between type A and type B thymomas.Methods:Illumina MethylationEPIC BeadChip(Infinium)microarray(850K)was used to detect the whole-genome DNA methylation profiling of thymic epithelial tumor.After differential methylation analyses,a set of differentially methylated CpGs were identified between thymoma and normal control,type A and type B thymoma,and myasthenia gravis-associated thymoma and thymoma.Integrative analysis was carried out by combination of the methylation array data of type A and type B thymoma with gene expression array data from GEO.Moreover,functional annotation analysis was performed on the corresponding differentially methylated genes using the GO and KEGG pathway enrichment methods.The receiver operating characteristic analyses were performed to assess the diagnostic value of candidate DNA methylation markers in type A and type B thymoma.Results:Differential methylation analyses revealed a global hypomethylation pattern in thymoma,including 119 hypermethylated DMCs and 18999 hypomethylated DMCs.A total of 10014 CpGs were differentially methylated(??>0.2)between type A and type B thymoma.Intergrative analysis showed that 36 genes had differentially methylated CpG sites in their promoter region and their gene expression patterns inverse to the direction of change in DNA methylation.Eleven genes(FEZ2,PTPRE,ATP2A2,CBLB,C5orf45,CPE,FSTL1,ZNF396,FRAS1,NAV2 and LCA5)were identified to have the potential diagnosis value fortype A and type B thymoma.Conclusion:Thymomas showed a global decrease in methylation when compared with adjacent normal control.Differentially methylated CpG sites were identified in the promoter regions of 36 genes and regulated.Eleven genes(FEZ2,PTPRE,ATP2A2,CBLB,C5orf45,CPE,FSTL1,ZNF396,FRAS1,NAV2 and LCA5)were identified to have the potential diagnosis value for type A and type B thymoma.