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Objectives: We previously reported a transthoracic approach using the da Vinci Single-Site™ platform. This study describes the outcomes of robotic single-site thymectomy via a subxiphoid approach based on our previous experiences., Methods: This study included patients, who underwent single-site robotic thymectomy via the subxiphoid approach between September 2018 and October 2019. A 3- to 4-cm vertical incision was made over the subxiphoid area, and the Lapsingle port with CO2 gas was introduced. After docking at the single site, a 5-mm curved cannula, 5-mm cardiere grasper and Maryland bipolar forceps or permanent cautery hook was inserted. The single-site robotic platform was used to conduct all surgical procedures except the dissection around the inferior portion of the thymic tissue performed via a thoracoscopic approach through the same incision., Results: Overall, 13 patients, including 2 with myasthenia gravis, were enrolled. The mean duration of the surgery and chest drainage were 167.3 ± 52.8 (range 73-253) min and 2.2 ± 0.9 (range 1-5) days, respectively. All surgeries were successfully completed without conversion to an open surgery, and there were no major post-surgical complications. The diagnoses based on histopathology included thymoma in 10 patients, thymolipoma in 2 patients and atypical carcinoid tumour in 1 patient with free resection margin., Conclusions: This study demonstrated that robotic single-site-assisted thymectomy via the subxiphoid approach is a safe and technically feasible procedure. Although this initial series comprised relatively simple cases, more advanced and complex procedures can soon be performed with the advent of single-port robotic platform., (© The Author(s) 2020. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Objectives: Thymectomy is the treatment of choice for thymomatous myasthenia gravis (MG) for both oncological and neurological aspects. However, only a few studies comprising small numbers of patients have investigated post-thymectomy neurological outcomes. We examined post-thymectomy long-term neurological outcomes and predictors of thymomatous MG using a multi-institutional database., Methods: In total, 193 patients (47.3 ± 12.0 years; male:female = 90:103) with surgically resected thymomatous MG between 2000 and 2013 were included. Complete stable remission (CSR) and composite neurological remission (CNR), defined as the achievement of CSR and pharmacological remission after thymectomy, were evaluated. Predictors for CSR and CNR were examined by Cox regression analysis., Results: The median duration between MG and thymectomy was 3.1 months. In addition, 161 patients (83.4%) had symptoms less than Myasthenia Gravis Foundation of America clinical classification III. All patients underwent an extended thymectomy; there were no perioperative deaths. The 10-year cumulative probability of CSR and CNR was 36.9% and 69.1%, respectively. Mild preoperative symptoms were a significant predictor for CSR (P = 0.040), and a large tumour was a predictor for CNR (P < 0.001). Patients with a large tumour were associated with early MG onset and no steroid treatment. Surgical methods, thymoma stage and histological subtypes were not associated with long-term neurological remission., Conclusions: Large tumour size and preoperative mild symptoms were predictors for long-term neurological outcome in thymomatous MG. Considering that patients with early onset of MG and no immunosuppressive treatment tend to have large tumours, early surgical intervention for patients with thymomatous MG having mild symptoms might be beneficial for controlling neurological outcomes., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Introduction: Surgical resection is a standard treatment for thymic malignancies. However, prognostic significance of nodal metastases and lymph node dissection remains unclear. The aim of this study is to determine prognostic significance of nodal metastases and the role of lymph node dissection (LND) in thymic malignancies., Methods: Between 2000 and 2013, 1597 patients who underwent thymectomy due to thymic malignancy were included. Predictive factors for nodal metastasis and prognostic significance of LND were evaluated. Patients were divided into two groups: (1) LND+ group, with intentional LND (446 patients, 27.9%); and (2) LND- group, without intentional LND (1151 patients, 72.1%). Propensity score matching was performed between the two groups., Results: Lymph node metastasis was identified in 20 (6.7%) of 298 patients with thymoma and 47 (31.7%) of 148 patients with thymic carcinoma. In multivariable analysis, thymic carcinoma (hazard ratio: 19.2, p < 0.001) and tumor size (hazard ratio: 1.09, p = 0.02) were significant predictive factors for lymph node metastasis. The 10-year freedom from recurrence rate of pN1 and pN2 was significantly worse than that of pN0 (p < 0.001). LND did not increase operative mortality or complication. There was no significant difference in 10-year freedom from recurrence rate between LND+ and LND- groups (82.4% versus 80.9%, p = 0.46 in thymoma; 45.7% versus 44.0%, p = 0.42 in thymic carcinoma)., Conclusions: Lymph node metastasis was a significant prognostic factor in thymic malignancies. Although LND did not improve long-term outcomes in thymic malignancies, LND played a role in accurate staging, and improved prediction of prognosis., (Copyright © 2018 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Objectives: To investigate the diagnostic value of dual-energy computed tomography (DECT) in differentiating between low- and high-risk thymomas and thymic carcinomas., Materials: Our institutional review board approved this study, and patients provided informed consent. We prospectively enrolled 37 patients (20 males, mean age: 55.6 years) with thymic epithelial tumour. All patients underwent DECT. For quantitative analysis, two reviewers measured the following tumour parameters: CT attenuation value in contrast Hounsfield units (CHU), iodine-related HU and iodine concentration (mg/ml). Pathological results confirmed the final diagnosis., Results: Of the 37 thymic tumours, 23 (62.2 %) were low-risk thymomas, five (13.5 %) were high-risk thymomas and nine (24.3 %) were thymic carcinomas. According to quantitative analysis, iodine-related HU and iodine concentration were significantly different among low-risk thymomas, high-risk thymomas and thymic carcinomas (median: 29.78 HU vs. 14.55 HU vs. 19.95 HU, p = 0.001 and 1.92 mg/ml vs. 0.99 mg/ml vs. 1.18 mg/ml, p < 0.001, respectively)., Conclusion: DECT using a quantitative analytical method based on iodine concentration measurement can be used to differentiate among thymic epithelial tumours using single-phase scanning., Key Points: • IHU and IC were lower in high-risk thymomas/carcinomas than in low-risk thymomas • IHU and IC were lower in advanced-stage thymomas than in early-stage thymomas • Dual-energy CT helps differentiate among thymic epithelial tumours.

Objectives: For early-stage thymoma, complete thymectomy has classically been regarded as the standard treatment protocol. However, several studies have shown that limited thymectomy may be an alternative treatment option for thymoma. This study compared perioperative outcomes, survival, and recurrence rates between patients undergoing limited thymectomy and complete thymectomy., Materials and Methods: Between January 2000 and December 2013, a total of 762 patients underwent thymectomy for stage I or II thymomas at four institutions participating in the Korean Association for Research on the Thymus. Patients were divided into two groups: limited thymectomy group (n=295) and complete thymectomy group (n=467). Comparative clinicopathological, surgical, and oncological features were reviewed retrospectively., Results: The median follow-up time was 49 months (range: 0.2-189 months). A propensity score-matching analysis, based on seven variables (age, sex, surgical approach, tumor size, WHO histological type, Masaoka-Koga stage, and adjuvant radiotherapy), was performed using 141 patients selected from each group. The 5- and 10-year freedom-from-recurrence rates in the limited thymectomy group were 96.3% and 89.7%, respectively, and those in the complete thymectomy group were 97.0% and 85.0%, respectively. No significant differences in these rates were observed between groups (p=0.86). A multivariate Cox regression analysis showed that overall survival and freedom-from-recurrence rates did not significantly differ by surgery extent (p=0.27, 0.66, respectively). Perioperative outcomes were better in the limited thymectomy group., Conclusion: Limited thymectomy was not inferior to complete thymectomy with respect to recurrence, and had better perioperative outcomes. Limited thymectomy may be a viable treatment option for early-stage thymoma., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Objectives: Recurrence of resected thymoma frequently occurs during follow-up, with pleural recurrence as the most common type. The aim of our study was to identify risk factors for pleural recurrence after complete resection of thymoma by investigating clinical, radiological, surgical, and pathological findings., Materials and Methods: Retrospective study was performed with 309 patients who had undergone complete resection of thymoma between January 2000 and December 2013. Among these cases, the patients were divided into the no pleural recurrence group (n=285) and the pleural recurrence group (n=24). Radiologic parameters such as maximum tumor diameter, tumor perimeter that contacted the lung (TPCL) and lobulated tumor contour were measured based on computed tomography. A multivariate analysis was performed to estimate risk factors for pleural recurrence including maximum tumor diameter, TPCL, lobulated tumor contour, World Health Organization (WHO) histologic classification, and Masaoka-Koga (M-K) stage., Results: The median follow-up period was 62 months. The pleural recurrence rate was 7.8% (24/309). After univariate analysis, longer maximum tumor diameter (p<0.001), longer TPCL (p<0.001), lobulated tumor contour (p=0.001), WHO histologic type B2, B3 (p=0.002), and M-K stage III/IV (p<0.001) demonstrated significant differences with risk factors of pleural recurrence. Multivariate analysis revealed that TPCL (per 1cm increase: hazard ratio [HR]: 1.040, 95% confidence interval [CI]: 1.019-1.061, p<0.001), lobulated tumor contour (HR: 5.883, CI: 1.201-28.824, p=0.029), WHO histologic classification B2/B3 (HR: 5.331, CI: 1.453-19.558, p=0.012) and advanced M-K stage (HR: 3.900, CI: 1.579-9.632, p=0.003) were significantly associated with pleural recurrence., Conclusion: TPCL and lobulated tumor contour as well as WHO histologic classification and M-K stage were independent predictors of pleural recurrence after thymoma resection. Our study demonstrated that radiologic parameters could be useful predictor of pleural recurrence in patients with resected thymoma., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Background: Complete resection of the thymus is considered appropriate for a thymoma resection because any remaining thymic tissue can lead to local recurrence. However, there are few studies concerning the extent of thymus resection. Therefore, we conducted a retrospective study to investigate whether recurrence following thymoma resection correlated to the extent of resection., Methods: Between 1986 and 2011, a total of 491 patients underwent resection of thymic epithelial tumors with curative intent. Of those, we excluded patients with an undetermined World Health Organization (WHO) histologic type, patients with type C thymoma, and patients who underwent incomplete resection (n = 21). The remaining 342 patients were reviewed retrospectively and compared recurrence according to the extent of resection., Results: Extended thymectomy was performed in 239 patients (69.9%) and limited thymectomy was performed 103 patients (30.1%). In the extended thymectomy group, 29 recurrences occurred, and in the limited thymectomy group, 10 recurrences occurred.Comparing rates of freedom from recurrence between two groups, there was no significant statistical difference in total recurrence (p = 0.472) or local recurrence (p = 0.798). After matching patients by stage and tumor size, there was no significant difference in freedom from recurrence between the two groups (p = 0.162). Additionally, after adjusting for histologic type and MG, there was also no significant difference (p = 0.125) between groups., Conclusions: No difference in the rate of recurrence was observed in patients following limited thymectomy compared with extended thymectomy.

Purpose: Recurrence rate is considered a better measure of clinical outcomes after thymoma resection than overall survival due to the indolent behavior of thymomas. This study was designed to determine predictors of recurrence after thymoma resection., Materials and Methods: A single-institution, retrospective study was performed, including 305 patients who had undergone thymoma resection between 1986 and 2009., Results: Among 305 patients, recurrence was observed in 41 patients (13.4%). The recurrence rates were 0% (0/19), 6.3% (4/63), 4.2% (2/48), 18.6% (11/59) and 20.7% (24/116) for type A, AB, B1, B2 and B3 tumors, respectively. The recurrence rate according to Masaoka stage was 6.1% (8/132), 11.4% (13/114), 26.8% (11/41) and 50.0% (9/18) for stages I, II, III and IV, respectively. After univariate analysis, completeness of resection (R0 versus R1), World Health Organization (WHO) histologic type (A, AB, B1 versus B2, B3), Masaoka stage, and size of tumor (<8 cm versus ≥8 cm) demonstrated significant differences with freedom from recurrence. Upon multivariate analysis, Masaoka stage was the only independent predictor of recurrence., Conclusion: WHO histologic type, Masaoka stage, and size of tumor were associated with recurrence. Particularly, Masaoka stage was the only independent predictor of recurrence after thymoma resection.

Introduction: Clinical outcomes and prognosis of recurrent thymoma are not well known because of its rarity and indolent clinical course. This study was designed to determine the clinical outcomes and prognosis of recurrent thymoma., Methods: Between 1986 and 2009, 41 of 305 patients who underwent resection for thymoma had recurrence. We reviewed those patients retrospectively., Results: Of 15 patients who underwent re-resection for recurrent thymoma, 13 patients (87%) achieved complete re-resection. Of 26 patients who did not undergo re-resection, 11 patients received chemotherapy, five received chemoradiotherapy, one received another treatment, and nine patients did not receive any treatment. World Health Organization histological types AB or B1 and complete re-resection were positive prognostic factors. The complete re-resection group had better survival after recurrence than the non/incomplete re-resection group (5-year survival rate: 90.9% versus 44.7%, p = 0.014). The complete re-resection group had comparable survival after initial resection of thymoma to the patients without recurrence (5-year, 10-year survival: 91.7%, 91.7% versus 90.7%, 86.5%, p = 0.618) and better survival compared with the non/incomplete re-resection group (5-year, 10-year survival: 91.7%, 91.7% versus 81.6%, 56.7%, p = 0.018)., Conclusions: World Health Organization histologic types AB or B1 and complete re-resection are favorable prognostic factors of recurrent thymoma. In particular, complete re-resection of recurrent thymoma contributes to better survival than other management. Therefore, we suggest that long-term surveillance extended at least 20 years may be essential for early detection of recurrence to increase the chance of complete re-resection of recurrent thymoma.

Background: This study aimed to introduce the authors' surgical technique of bilateral video-assisted thoracoscopic thymectomy (BVT) and to compare their early surgical results between BVT and transsternal extended thymectomy (T3-b thymectomy) for patients with myasthenia gravis (MG)., Methods: The records of 114 patients who underwent either BVT (n = 55) or T3-b thymectomy (n = 59) for MG were reviewed retrospectively between January 2006 and November 2009., Results: No surgical mortality or major morbidity occurred in either group. There was no conversion to open thymectomy, and no statistical difference was found in operation time between the two groups (112.2 ± 26.2 min for BVT vs. 130.7 ± 27.3 min for T-3b; p = 0.908). The duration of the chest tube, the length of the intensive care unit (ICU) or hospital stay, and the duration of opioid use for pain control were shorter in BVT group. The estimated blood loss and the total amount of drainage were greater in the T3-b thymectomy group. The specimen weights retrieved by BVT (72.5 ± 61.6 g) were similar to those retrieved by T3-b thymectomy (74.1 ± 38.2 g, p = 0.63) in nonthymomatous MG., Conclusions: The BVT was a safe procedure with a surgical extent and amount similar to those of T-3b thymectomy and less invasive for patients with MG. Long-term follow-up assessment and more extensive data are mandatory to verify the early surgical outcomes.

Information regarding prognosis of thymoma patients stratified by both World Health Organization classification and Masaoka staging system is very limited. Analyze 5-year survival data from a large number of thymoma patients stratified by both World Health Organization histologic type and Masaoka stage using meta-analysis. Perform power analysis to estimate the number of cases that would be needed to test the null hypothesis to a power of 80%. Five-year survival data from 905 thymoma patients treated with thymectomy at seven hospitals in America, Japan, Korea, India, Italy, and Germany. Survival data was reported as "dead" or "alive" to facilitate meta-analysis. Significant differences were detected only when comparing survival rates of thymoma patients in stages I to III with those of stage IV disease. Analysis by World Health Organization histologic type and stage yielded significant differences only in patients with thymomas A vs. B2 and A vs. B3 in stage III disease. No significant data heterogeneity was detected with funnel plots and Egger's regression test. Power analysis estimated that a study with 7077 patients is needed to evaluate the prognostic significance of all thymomas stratified by both World Health Organization histologic type and stage to a power of 80%. Selected World Health Organization histologic types are significantly associated with prognosis in stage III thymoma patients and may help select individuals benefiting from neoadjuvant therapy. Power analysis shows that studies with much larger number of patients are needed to exclude the possibility that histologic type may provide significant prognostic information in other stages of the disease., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Thymic epithelial tumors (TETs) consist of a series of neoplasm that differ morphologically and biologically. Due to its rarity and indolent natural history, large-scale prospective trials have been lacking. This study aimed to evaluate long-term clinical outcomes and clinicopathologic features for TET after surgical resection and adjuvant treatments. One hundred patients who received surgery plus adjuvant radiotherapy +/- chemotherapy for TET (Masaoka stage II-IVa) from 1995 to 2005 were retrospectively reviewed. Masaoka staging systems were adopted, and pathologic results were classified according to World health organization (WHO) histologic classification. After surgery, 55 patients were treated with radiotherapy alone, while 45 with radiotherapy and chemotherapy. The median radiation dose was 50.4 Gy (45-63 Gy) and six cycles of chemotherapy, consisting of doxorubicin, cisplatin, vincristine and cyclophosphamide, were applied every 3-4 weeks. Distributions according to Masaoka stage were as follows; stage II (58 patients), III (21) and IVa (21). According to WHO histology, there were A (3), AB (7), B1 (7), B2 (31), B3 (31) and C (21). With a median follow-up duration of 65 months (8-143 months), the 5-year overall survival (OS) and disease-free survival (DFS) rates were 75.7% (89.2, 67.9 and 52.1% in stage II, III and IVa, respectively) and 70.3% (83, 62.4 and 33.6% in stage II, III and IVa, respectively). In multivariate analysis, prognostic factors for OS were age, WHO histology, Masaoka stage, and recurrence, while pleural involvement, WHO histology, and Masaoka stage had significant impacts on DFS. Adjuvant chemotherapy did not alter survival outcomes and recurrence patterns. Pleura was the most common recurrence site (15 patients, 53.6%), and significantly associated with pleural recurrence-free survival. In conclusion, pleural involvement at diagnosis was the important prognostic factor, in addition to WHO histology and Masaoka stage. To prevent pleural recurrence and prolong survival, innovative therapeutic approaches warrant further investigations.

Objective: Neurotrophins are known to exert a variety of pleiotropic responses in different target tissues, but little is known about their effect on thymic epithelial tumors. Therefore, we analyzed the expression of neurotrophin receptors in surgically resected thymic epithelial tumors and evaluated their clinical relevance., Methods: The expression of neurotrophin receptors (Trk-A, Trk-B, Trk-C and p75(NTR)) in thymic epithelial tumors was evaluated in 99 consecutive patients based on immunohistochemical staining. The pattern of expression was analyzed according to the WHO classification, and survival outcomes were estimated., Results: Thymic tumors were classified as type A (n=6), AB (n=21), B1 (n=15), B2 (n=24), B3 (n=22) or C (n=11). All tumors, except one type C thymoma, demonstrated cytoplasmic Trk-A immunostaining, and no thymic tumors showed Trk-B or Trk-C immunoreactivity. p75(NTR) immunostaining demonstrated characteristic patterns according to the WHO subtypes of thymomas. All type A and type AB thymomas showed p75(NTR) immunoreactivity, except one type A tumor. The expression of p75(NTR) was negative in 6 patients (40%) with type B1 thymomas, 19 patients (79.2%) with type B2 thymomas, 17 patients (77.3%) with type B3 thymomas and 10 patients (90.9%) with type C thymomas. Tumor-related survival at 5 and 10 years was 95.5 and 89.5%, respectively, in p75(NTR)-positive thymomas and 82.8 and 77.2%, respectively, in p75(NTR)-negative thymomas; however, the differences were not statistically significant (P=0.14)., Conclusions: Among the neurotrophin receptors examined, the pattern of p75(NTR) expression closely correlated with the WHO subtypes of thymomas. Further study of p75(NTR) expression may aid in understanding the biology of thymic epithelial tumors.

Study Objectives: Controversy has ensued about the prognostic relevance of the new World Health Organization (WHO) schema for the classification of thymoma. In this study, we present the clinical and histologic features of 108 thymomas and evaluate the usefulness of this histologic schema in view of the prognosis., Design: Retrospective, clinicopathologic analysis of our experience and a review of recent literature., Setting: Department of Thoracic and Cardiovascular Surgery of a university hospital., Methods: A series of 108 thymomas were reviewed and classified by the new WHO schema. The clinical characteristics and the survival outcome were investigated in reference to the WHO subtypes. The Cox proportional hazards model was applied to determine the factors affecting the tumor-related survival. Recent literature on the prognostic relevance of the WHO schema was reviewed., Results: There were 7 type A tumors, 25 type AB tumors, 12 type B1 tumors, 32 type B2 tumors, 20 type B3 tumors, and 12 type C tumors. The histologic subtype closely correlated with the Masaoka stage (p = 0.00). The tumor-related survivals at 5 years and 10 years were 88.0% and 77.9%, respectively. Stage III and IV tumors had a significantly worse prognosis than stage I or II tumors (p < 0.05). Type B3 tumors had an intermediate prognostic ranking in comparison with the carcinomas and with the other groups. On multivariate analysis, the WHO subtype (A-B2 vs B3 vs C) could predict the tumor-related survival, but the Masaoka stage was the most important prognostic factor affecting the postoperative survival (p = 0.026)., Conclusion: The Masaoka stage is the most important determinant of survival in surgically resected cases of thymoma. To clarify the prognostic relevance and clinical usefulness of the WHO schema, consistent parameters reflecting the surgical outcome and development of the diagnostic tools that could improve the interobserver agreement within type B are needed.