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Background: We believe the merit of preservation of a part of the thymus following surgery for thymoma. We evaluated the efficacy of partial or subtotal thymectomy for early-stage thymoma in the prospective study., Methods: The Japanese Association for Research on the Thymus conducted a multiple institutional study of thymectomy for thymoma localized in the thymus without total thymectomy. Patients without autoimmune disease who had an anterior mediastinal tumor that had been clinically diagnosed as an early-stage thymoma were enrolled in the study. Patients who were positive for anti-acetylcholine receptor antibodies were excluded., Results: Sixty-three patients were enrolled preoperatively; 27 patients were judged as being inappropriate based on the other thymic pathologies or tumor invasion. The remaining 36 cases were diagnosed as early-staged thymoma and analyzed. The mean age of the patients was 61 years. The mean maximal tumor diameter in the resected specimens was 3.6 cm. The most common pathological types of thymoma were AB (n = 10) and B1 (n = 10). The Masaoka stages were classified as stage I (n = 22) and II (n = 14). The mean observation period was 63 months. Two patients died due to respiratory dysfunction, which was not related to thymoma. One hundred percent of the patients remained recurrence-free., Conclusions: This prospective study suggested the efficacy of partial or subtotal thymectomy for early-stage thymoma in patients without any apparent evidence of autoimmune disease. We can preserve a part of the thymus even following surgery for thymoma to prepare the possible second malignancies or diseases in future.

Anterior chest wall lifting facilitates a wide view and allows easy access during thoracoscopic surgery in a supine position for anterior mediastinal lesions. We previously reported an anterior chest wall lifting method for a thymectomy that utilizes our original costal hooks. Here, we present a less invasive method that can be performed with only a needle puncture, i.e., a metal plate placed under the ribs is lifted with a wire inserted through the anterior chest wall. We have applied this novel 'T-lifting method' for 5 different cases with anterior mediastinal tumors, and found it to be simple and easy to perform, as well as less invasive for patients undergoing thoracoscopic surgery.

Introduction: We previously introduced video-assisted thoracoscopic ET (VATS-ET) as a therapeutic option for MG with acceptable results. We have conducted further investigations to improve the procedure without deterioration of operative results, including myasthenia gravis (MG) remission rate and palliation rate. Here, we report the details of our current procedure, as well as surgical results and patient outcomes as compared with the original VATS-ET procedure., Material and Methods: From January 2002 to September 2013, we performed a VATS-ET procedure with an anterior chest wall lifting method for 77 patients who had MG with or without a thymoma. During that period, we investigated the appropriate indications and improved the procedure., Results: Our current indication for this procedure is MG with the anti-acetylcholine receptor antibody or sero-negative type, or MG with a thymoma <5 cm in diameter without invasion to adjacent organs. With our procedure, the thymus and surrounding tissue are sufficiently resected using a bilateral thoracoscopic surgical method without neck incision. Remission and palliation rates were found to be equivalent to those obtained with the original VATS-ET procedure., Conclusion: VATS-ET is suitable for select patients with MG with or without a thymoma. In addition, our current method has shown to be effective while also offering cosmetic advantages as compared with the original, neck incision needed, VATS-ET method.

Objectives: Although video-assisted thoracoscopic thymectomy (VATS-Tx) for thymoma has been introduced, its oncological outcome remains unclear. Our institutional experience with early-stage thymoma was retrospectively reviewed to evaluate the oncological feasibility of thoracoscopic thymectomy., Methods: A retrospective review consisting of 74 patients with Masaoka Stage I and II thymomas who had undergone thymectomy was performed. Forty-five patients underwent thoracoscopic thymectomy, while 29 underwent thymectomy through the open sternotomy approach. The clinical factors associated with the surgical outcome, including tumour recurrence, were investigated., Results: Neither operative death nor major postoperative complications were observed. The median intraoperative blood loss and operative time of thoracoscopic thymectomy were 50 ml and 180 min, respectively. Among the patients with thymomas >5 cm, the number of patients with operative time >4 h was 9 of 26 (34.6%) in the thoracoscopic thymectomy and 1 of 21 (4.8%) in the open sternotomy groups. Pleural recurrence was observed in 3 (6.7%) patients with thymoma >5 cm only in the thoracoscopic thymectomy group. Tumour capsule injury by manipulation during the operation was recorded in 2 of these 3 patients. In 2 of the 3 cases who had tumours with cystic portions on computed tomography, a tumour capsule injury occurred due to manipulation during thoracoscopic thymectomy., Conclusions: VATS-Tx for early-stage thymomas is feasible, while the indications should be carefully considered in patients with large or cystic tumours. The conventional open sternotomy approach could be recommended in patients with thymomas >5 cm to avoid capsule injury.

Myasthenia gravis (MG) is an autoimmune disease mediated by autoantibodies to the striated muscle tissue. It is often treated by thymectomy. We review recent studies to investigate the biological implications of thymectomy. In anti-acetylcholine receptor antibody (anti-AchR Ab)-positive patients without a thymoma, abnormal germinal center formation in the thymus seems to play an essential role in the pathogenesis of MG. Specific differentiation of B cells producing anti-AchR Ab takes place uniquely in the thymus, and thymectomy is thought to assist in terminating the provision of high-affinity anti-AchR antibody-producing cells to peripheral organs. Thymectomy is not indicated for anti-AchR Ab-negative MG patients who are antimuscle specific kinase antibody (anti-MuSK Ab)-positive, although some anti-MuSK Ab-negative patients may benefit from the procedure. A thymoma can be considered as an acquired thymus with insufficient function of negative selection. The resection of a thymoma is thought to terminate the production of self-reactive T cells. Thus, the biological implications of thymectomy for MG have been partially revealed. Nevertheless, additional studies are needed to elucidate the ontogeny of T cells that recognize AchR and the mechanism of the activation of anti-AchR antibodies producing B cells.

Minimally invasive thymectomy procedures have been proposed for nonthymomatous myasthenia gravis. However, few reports stressed that the lower invasiveness or cosmetic benefits also evaluated the rationale of a thymectomy, which is performed to remove as much thymic tissue as possible. We retrospectively reviewed 30 consecutive patients who underwent a bilateral video-assisted thoracoscopic extended thymectomy (VATET) and compared the results with those of 26 patients who underwent a transsternal extended thymectomy (TSET) to determine the amount of removed thymic tissue and clinical prognosis. The amount of blood loss during the operation for VATET (median 60 mL; range nearly 0 to 940 mL) was significantly lower as compared with that of TSET. The median weight of removed thymic tissue (37.0 g; 18.3 to 100.0 g) and remission rates (1 y: 12.5%; 3 y: 30.8%; 4 y: 44.4%) of VATET were comparable with those of TSET. The VATET group had a similar amount of thymo-fatty tissue removed and feasible clinical outcomes as compared with the TSET group, indicating that VATET provides a proper balance between less invasiveness and radical capability.

Currently, no specific item regarding endoscopic thymectomy for nonthymomatous myasthenia gravis is listed in the standards of deciding medical service fees. To understand the present situation regarding the medical fee-for-service for endoscopic thymectomy, a questionnaire survey was conducted involving the institutions and members participating in the Japanese Association for Research on the Thymus. Of 101 responding institutions, 18 (18%) reported basically performing endoscopic thymectomy in all qualifying patients, and 32% of the institutions reported mainly performing median sternotomy but sometimes performing endoscopic thymectomy. The methods of approaching endoscopic thymectomy varied among the institutions, but most included endoscopic clips or ultrasound-driven scalpels as well as anterior chest wall lifting devices. A total of 214 patients underwent thymectomy in 2004 in the responding institutions, of whom 77 patients (32%) underwent endoscopic thymectomy. In total, 71% of the responding institutions answered that a specific item regarding endoscopic thymectomy should be listed in the standards for deciding medical service fees.

Background: Because evidence-based data regarding the quality of video-assisted thoracoscopic thymectomy for the treatment of myasthenia gravis are lacking, a prospective trial comparing three different operative approaches was conducted to evaluate their efficacy., Methods: This prospective study enrolled 20 consecutive patients with nonthymomatous myasthenia gravis. A series of three approaches for bilateral video-assisted thoracoscopic extended thymectomy (VATET) using the anterior chest wall-lifting method (original), the original method with a flexed-neck position (modified), and the original method with a transcervical approach (final) were prospectively performed in each patient for quantitative and pathologic evaluation of the residual thymus after each approach., Results: Complete VATET required 242 +/- 48 min, with the transcervical procedure requiring 23 +/- 12 min. After the modified method, the residual thymus in the cervical region was 1.5 cm in size and weighed 0.8 g (0.8% of the entire thymus), as compared with a size of 2.2 cm and a weight of 1.3 g (3.2%) after the original method. Each value is the result of comparison with the final method. Histopathologic studies showed residual tissue in the germinal center as well as Hassall's corpuscles in more than 70% of cases., Conclusion: The findings show that VATET without the transcervical approach could be an immunologically incomplete treatment for myasthenia gravis. Therefore, the transcervical approach should be included in VATET procedures to ensure radicality.

Background: Video-assisted thoracoscopic (VATS) thymectomy has been applied as a surgical option for autoimmune myasthenia gravis. Prior identification and fine division of the thymic veins are critical to the prevention of unexpected severe bleeding that may require conversion to open surgery. Until recently, such bleeding could be avoided only by meticulous dissection of thymic fat tissue away from the left brachiocephalic vein (LBV). With recent advances in computed tomography (CT), multidetector-row computed tomography (MDCT) can readily be obtained and provides three-dimensional (3D) images. This study explored its value for preoperative identification of the thymic veins draining into the LBV, and thus for prevention of injury to these veins during endoscopic thymectomy., Methods: Five patients with myasthenia gravis, thymoma, or both underwent enhanced MDCT preoperatively. The thymic veins draining into the LBV were visualized using both horizontal and sagittal/coronal CT images. Then 3D images were reconstructed to enable operators to simulate endoscopic views. During each VATS extended thymectomy, the numbers and branching patterns of the thymic veins were compared with the preoperative MDCT images., Results: The thymic veins draining into the LBV were clearly identified with MDCT in all five patients examined. Reconstructed 3D images clearly located their courses in the thymic/fat tissue and their entry routes into the LBV, thus simulating the actual intraoperative endoscopic views. All tributaries divided during surgery were identified preoperatively with MDCT., Conclusions: Location of thymic veins with MDCT can provide precise preoperative information about thymic venous anatomy. This easy and less invasive examination has the potential to make VATS thymectomy easier and safer.

Background and Purpose: Thymectomy is generally accepted as the major option of treatment for myasthenia gravis. To elucidate the biological role of thymectomy in the treatment of myasthenia gravis, the immunologic characteristics of the thymus was studied in association with the postoperative kinetics of the anti-acetylcholine receptor antibody titer., Materials and Methods: Thirty-four patients with nonthymomatous myasthenia gravis who had positive anti-acetylcholine receptor antibody titer and undergoing extended thymectomy were subjected to the study. Reduction of anti-acetylcholine receptor antibody titer was evaluated in terms of the proportion of anti-acetylcholine receptor antibody titer at 1 year after thymectomy to that before the operation. The numbers of B lymphocytes (CD19(+) cells) and the germinal center B lymphocytes (CD19(+)CD38(high) cells) present in 1 g of the thymic tissue were calculated by flow cytometry., Results: The proportion of anti-acetylcholine receptor antibody titer at 1 year after thymectomy ranged from 27.5% to 150%. The numbers of B lymphocytes and the germinal center B lymphocytes in 1 g of the thymic tissue ranged from 0.19 x 10(6)/g to 162.8 x 10(6)/g and from 0.09 x 10(6)/g to 33.4 x 10(6)/g, respectively. The proportion of anti-acetylcholine receptor antibody titer at 1 year after thymectomy had a significant inverted correlation with the number of B lymphocytes (P =.002) as well as that of the germinal center B lymphocytes (P =.007)., Conclusion: Effectiveness of thymectomy was dependent on predominance of B lymphocytes and the germinal center B lymphocytes in the thymus, suggesting that one of the biological roles of thymectomy in the treatment of myasthenia gravis is removing the thymus-associated germinal centers.