Postthymectomy Myasthenia Gravis: Relationship With Thymoma and Antiacetylcholine Receptor Antibody

Does Surgical Removal of the Thymus Have Deleterious Consequences?

The role of immunosenescence, particularly the natural process of thymic involution during aging, is increasingly acknowledged as a factor contributing to the development of autoimmune diseases and cancer. Recently, a concern has been raised about deleterious consequences of the surgical removal of thymic tissue, including for patients who undergo thymectomy for myasthenia gravis (MG) or resection of a thymoma. This review adopts a multidisciplinary approach to scrutinize the evidence concerning the long-term risks of cancer and autoimmunity postthymectomy. We conclude that for patients with acetylcholine receptor antibody-positive MG and those diagnosed with thymoma, the removal of the thymus offers prominent benefits that well outweigh the potential risks. However, incidental removal of thymic tissue during other thoracic surgeries should be minimized whenever feasible.

Unique association of anti-GABAA receptor encephalitis and myasthenia gravis in a patient with type A thymoma

Association between anti-GABAAR encephalitis and myasthenia gravis is extremely rare with few reported cases. Herein, we report a case of a female patient diagnosed with anti-GABAAR encephalitis and thymoma at the first admission. She was administered glucocorticoids for long-term immunotherapy, and thymectomy with biopsy demonstrated a type A thymoma. After 4 months, the symptoms of encephalitis were relieved, but she then developed post-thymectomy myasthenia gravis with anti-AChR and anti-titin dual positivity. Antibodies to connective tissue (anti-ANA, anti-PCNA) and those characteristics of paraneoplastic syndrome (anti-Ma2/Ta) were also positive. She received oral glucocorticoids and tacrolimus as immunosuppressive therapy, and myasthenic symptoms were stable during a 2-year follow-up. Our case revealed that anti-GABAAR encephalitis and myasthenia gravis can appear in patient with type A thymoma at different periods, which alerts physicians to take long-term follow-up for anti-GABAAR encephalitis with thymoma, even after thymectomy. Concurrent positivity for more than one antibody after thymectomy is rarely observed, and their contribution to the clinical course and treatment decision remains to be further investigated.

Germinal centers are associated with postthymectomy myasthenia gravis in patients with thymoma

BACKGROUND AND PURPOSE

Germinal centers (GCs) can be observed in the thymic tissues of patients with thymoma-associated myasthenia gravis (MG). Although an association between thymic GCs and MG has been suggested, it is unknown whether the presence of GCs could predict the development of MG after the resection of thymoma, known as postthymectomy MG.

METHODS

We conducted a retrospective analysis of previously nonmyasthenic patients who underwent surgical removal of the thymoma. All available thymic tissue slides were rereviewed by a pathologist to assess for GCs. Patients were classified into GC-positive and GC-negative groups based on the presence of GCs. The incidence of postthymectomy MG was compared between the two groups, and the risk factors for postthymectomy MG were assessed.

RESULTS

Of the 196 previously nonmyasthenic patients who underwent thymoma resection, 21 were GC-positive, whereas 175 were GC-negative. Postthymectomy MG developed in 11 (5.6%) patients and showed a higher incidence in the GC-positive group than in the GC-negative group (33.3% vs. 2.3%, p < 0.001). No postoperative radiotherapy and the presence of GCs were risk factors for postthymectomy MG in the univariate analysis. In multivariate analysis, invasive thymoma (hazard ratio [HR] = 9.835, 95% confidence interval [CI] = 1.358-105.372), postoperative radiotherapy (HR = 0.160, 95% CI = 0.029-0.893), and presence of GCs (HR = 15.834, 95% CI = 3.742-67.000) were significantly associated with postthymectomy MG.

CONCLUSIONS

Thymic GCs may be a significant risk factor for postthymectomy MG. Even in patients with thymoma who do not show clinical symptoms of MG, postthymectomy MG should be considered, especially if thymic GCs are observed.

Circulating miRNAs drive personalized medicine based on subgroup classification in myasthenia gravis patients

Myasthenia gravis (MG) is a classic autoimmune neuromuscular disease with strong clinical heterogeneity. The concept of subgroup classification was proposed to guide the precise treatment of MG. Subgroups based on serum antibodies and clinical features include ocular MG, early-onset MG with AchR antibodies, late-onset MG with AchR antibodies, thymoma-associated MG, MuSK-associated MG, LRP4-associated MG, and seronegative MG. However, reliable objective biomarkers are still needed to reflect the individualized response to therapy. MicroRNAs (miRNAs) are small non-coding RNA molecules which can specifically bind to target genes and regulate gene expression at the post-transcriptional level, and then influence celluar biological processes. MiRNAs play an important role in the pathogenesis of autoimmune diseases, including MG. Several studies on circulating miRNAs in MG have been reported. However, there is rare systematic review to summarize the differences of these miRNAs in different subgroups of MG. Here, we summarize the potential role of circulating miRNAs in different subgroups of MG to promote personalized medicine.

Risk factors for postoperative myasthenia gravis in patients with thymoma without myasthenia gravis: A systematic review and meta-analysis

Introduction

According to the principle, thymomas combined with myasthenia gravis (MG) require surgical treatment. However, patients with non-MG thymoma rarely develop MG and early- or late-onset MG after surgery is called postoperative MG (PMG). Our study used a meta-analysis to examine the incidence of PMG and risk factors.

Methods

Relevant studies were searched for in the PubMed, EMBASE, Web of Science, CNKI,and Wanfang databases. Investigations that directly or indirectly analyzed the risk factors for PMG development in patients with non-MG thymoma were included in this study. Furthermore, risk ratios (RR) with 95% confidence intervals (CI) were pooled using meta-analysis, and fixed-effects or random-effects models were used depending on the heterogeneity of the included studies.

Results

Thirteen cohorts containing 2,448 patients that met the inclusion criteria were included. Metaanalysis revealed that the incidence of PMG in preoperative patients with non-MG thymoma was 8%. Preoperative seropositive acetylcholine receptor antibody (AChR-Ab) (RR = 5.53, 95% CI 2.36 - 12.96, P<0.001), open thymectomy (RR =1.84, 95% CI 1.39 - 2.43, P<0.001), non-R0 resection (RR = 1.87, 95% CI 1.36 - 2.54, P<0.001), world health organization (WHO) type B (RR =1.80, 95% CI 1.07 - 3.04, P= 0.028), and postoperative inflammation (RR = 1.63, 95% CI 1.26 - 2.12, P<0.001) were the risk factors for PMG in patients with thymoma. Masaoka stage (P = 0.151) and sex (P = 0.777) were not significantly associated with PMG.

Discussion

Patients with thymoma but without MG had a high probability of developing PMG. Although the incidence of PMG was very low, thymectomy could not completely prevent the occurrence of MG. Preoperative seropositive AChR-Ab level, open thymectomy, non-R0 resection, WHO type B, and postoperative inflammation were risk factors for PMG.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022360002.

Poor responses and adverse outcomes of myasthenia gravis after thymectomy: Predicting factors and immunological implications

Myasthenia gravis (MG) has been recognized as a series of heterogeneous but treatable autoimmune conditions. As one of the indispensable therapies, thymectomy can achieve favorable prognosis especially in early-onset generalized MG patients with seropositive acetylcholine receptor antibody. However, poor outcomes, including worsening or relapse of MG, postoperative myasthenic crisis and even post-thymectomy MG, are also observed in certain scenarios. The responses to thymectomy may be associated with the general characteristics of patients, disease conditions of MG, autoantibody profiles, native or ectopic thymic pathologies, surgical-related factors, pharmacotherapy and other adjuvant modalities, and the presence of comorbidities and complications. However, in addition to these variations among individuals, pathological remnants and the abnormal immunological milieu and responses potentially represent major mechanisms that underlie the detrimental neurological outcomes after thymectomy. We underscore these plausible risk factors and discuss the immunological implications therein, which may be conducive to better managing the indications for thymectomy, to avoiding modifiable risk factors of poor responses and adverse outcomes, and to developing post-thymectomy preventive and therapeutic strategies for MG.

Pathological tumor long-to-short axis ratio as a prognostic factor in patients with thymic epithelial tumors

Background

Thymic epithelial tumors (TETs) exhibit irregular shapes reflective of the heterogeneity in tumor growth and invasive properties. We aimed to identify the prognostic value of the pathological tumor long‐to‐short axis (L/S) ratio in TETs.

Methods

A retrospective study was performed on patients with TETs who underwent extended thymectomy between January 1999 and December 2019 in our institute. Patients were divided into two groups according to the threshold of the L/S ratio. Overall survival (OS) and progression‐free survival (PFS) were evaluated by Kaplan‐Meier analysis. The independent prognostic factors of TETs were identified by multivariate analysis. The performance of prediction models for the above survival outcomes with and without the L/S ratio was evaluated using an integrated time‐dependent area under the curve (iAUC).

Results

Eligible patients were divided into two groups based on higher (n = 42) and lower (n = 94) L/S ratios according to a threshold value of 1.39. A significant difference was found between the two groups only in disease progression (p = 0.001). Poorer survival outcomes were found from Kaplan‐Meier curves in the higher L/S ratio group (p < 0.05). In the multivariable analysis, the L/S ratio showed significant effects on OS and PFS (p < 0.05). The performance of models with the L/S ratio was better than that without the L/S ratio in predicting survival outcomes.

Conclusions

The pathological tumor L/S ratio is an independent prognostic factor for OS and PFS in patients with TETs, and an L/S ratio >1.39 is associated with worse survival outcomes.

Refractory post-thymectomy myasthenia gravis with onset at MGFA stage V: a case report

BACKGROUND

Post-thymectomy myasthenia gravis (PTMG) is defined as thymoma patients without signs of myasthenia gravis (MG) pre-operation, but develop MG after radical surgical resection. PTMG might be misdiagnosed not only because of its rare incidence, but also the uncertain interval between the removal of thymoma and the new onset MG. Additionally, some surgeons and anesthesiologists pay less attention to those asymptomatic thymoma patients in perioperative management, leading to the neglect of new onset PTMG, and miss the best time to treat it.

CASE PRESENTATION

Majority of cases of PTMG with onset at stage I-II on the basis of Myasthenia Gravis Foundation of America (MGFA) classification have been reported, but rarely at stage V, which requiring intubation or non-invasive ventilation to avoid intubation. Herein, we presented a 70-year-old male with PTMG onset at MGFA stage V, meanwhile, he had severe pulmonary infection interfering with the diagnosis of PTMG, and eventually progressed to refractory PTMG, which requiring much more expensive treatments and longer hospital stays.

CONCLUSION

In the perioperative management of asymptomatic thymoma patients, careful preoperative evaluation including physical examination, electrophysiological test and acetylcholine receptor antibodies (AChR-Ab) level should be done to identify subclinical MG. Complete resection should be performed during thymectomy, if not, additional postoperative adjuvant therapy is neccessary to avoid recurrence. It's important to identify PTMG at a early stage, especially when being interfered with by postoperative complications, such as lung infection, so that treatments could be initiated as soon as possible to avoid developing to refractory PTMG.

Post-thymectomy myasthenia gravis: a case report and systematic review of literature

Myasthenia gravis (MG) is an autoimmune condition affecting the neuromuscular junction characterised by weakness and fatiguability, carrying a high morbidity if treatment is delayed. A clear association with thymoma has led to management with thymectomy as a common practice, but MG presenting post-thymectomy has rarely been reported. We present a case of an 82- year-old woman developing fatigue, ptosis and dysarthria 3 months after thymectomy. After a clinical diagnosis of MG was made, she responded well to prompt treatment with prednisolone and pyridostigmine. Her anti-acetylcholine receptor antibody (anti-AChR) subsequently came back positive. Our systematic review reveals that post-thymectomy MG can be categorised as early-onset or late-onset form with differing aetiology, and demonstrated correlation between preoperative anti-AChR titres and post-thymectomy MG. The postulated mechanisms for post-thymectomy MG centre around long-lasting peripheral autoantibodies. Clinicians should actively look for MG symptoms in thymoma patients and measure anti-AChR preoperatively to aid prognostication.

Difficult Decisions in Minimally Invasive Surgery of the Thymus

A minimally invasive resection of thymomas has been accepted as standard of care in the last decade for early stage thymomas. This is somewhat controversial in terms of higher-staged thymomas and myasthenia gravis patients due to the prognostic importance of complete resections and the indolent characteristics of the disease process. Despite concerted efforts to standardize minimally invasive approaches, there is still controversy as to the extent of excision, approach of surgery, and the platform utilized. In this article, we aim to provide our surgical perspective of thymic resection and a review of the existing literature.

Relationship between anti-acetylcholine receptor antibodies and the development of post-thymectomy myasthenia gravis in patients with thymoma: a single-center experience

Background

Approximately 15-29.6% of patients with thymoma have myasthenia gravis (MG). Some of these patients develop MG after thymectomy despite having no history of MG or related symptoms. Few previous studies have examined the risk factors for the development of post-thymectomy MG in patients with thymoma. Herein, we retrospectively reviewed our institutional experience with patients with thymoma who developed MG after thymectomy.

Methods

Twenty-six patients with thymoma but without MG, who were tested preoperatively for anti-acetylcholine receptor antibody (anti-AChR-Ab) levels, underwent surgical resection at our hospital between 2013 and 2020. Patients with thymic carcinoma were excluded from the study. We evaluated the association of outcomes with preoperative anti-AChR-Ab levels and post-thymectomy MG. We performed a χ² test for bivariate analysis of categorical data. Differences were considered significant at P<0.05.

Results

The characteristics of the 26 patients (median age: 62 years; 8 men, 18 women) were as follows: World Health Organization (WHO) classifications AB (n=8), B1 (n=9), B2 (n=6), B3 (n=1), and others (n=2) and Masaoka stage I (n=12), II (n=9), III (n=3), and IVa (n=2). Among the 26 patients, only five had high (>0.3 nmol/L) preoperative anti-AChR-Ab levels. Post-thymectomy MG occurred in two of the five patients (40%) with high preoperative anti-AChR-Ab levels. A high preoperative serum anti-AChR-Ab titer was significantly associated with post-thymectomy MG (P=0.0267). The anti-AChR-Ab titer was also measured postoperatively in four of the five (80%) patients with high preoperative levels. The anti-AChR-Ab titer decreased in two of these four patients, and neither developed postoperative MG.

Conclusions

Preoperative and postoperative anti-AChR-Ab positivity might be associated with post-thymectomy MG. Therefore, regular measurement of anti-AChR-Ab levels after thymectomy is required.

No correlation between acetylcholine receptor antibody concentration and individual clinical symptoms of myasthenia gravis: A systematic retrospective study involving 67 patients

OBJECTIVE

To investigate the correlation between acetylcholine receptor antibodies (AChR-Ab) concentration levels and individualized clinical symptoms in patients with AChR myasthenia gravis (AChR-MG) in China.

METHODS

ELISA was used to determine the concentration of AChR-Ab in patients with MG. The Myasthenia Gravis Foundation of America (MGFA) Clinical Classification, Quantitative Myasthenia Gravis (QMG) score, and MG-specific activities of daily living (MG-ADL) scoring systems were used to evaluate the clinical status of patients. Spearman correlation analysis was used to determine the correlation between the AChR-Ab concentration and clinical score. The changes in the antibody concentration and clinical score are shown in MGFA-antibody concentration-treatment plots.

RESULTS

Autoantibody detection tests were performed in 67 patients, and their clinical scores were recorded. Forty-nine patients received immunosuppressive therapy, 17 patients received pyridostigmine only, and 1 patient under thymectomy without any medication. The AChR-Ab concentration correlated with the MGFA Classification in 5 (29.4%) patients in the pyridostigmine-only group and 15 (30.6%) patients in the immunosuppressive drug group. The changes in the MGFA Classification preceded the changes in the AChR-Ab concentration in 4 (23.5%) patients treated with pyridostigmine and 10 (20.4%) patients on immunosuppressive drugs. In patients on oral non-steroidal immunosuppressants, the AChR-Ab concentration changed by more than 50%, whereas the MGFA Classification did not increase. The AChR-Ab concentration decreased in 17/32 (53.1%) patients after thymectomy, and then increased, whereas the AChR-Ab concentration increased in 15/32 (46.9%) patients and the MGFA Classification decreased in 27/32 (81.8%) patients after thymectomy. The AChR-Ab concentration presented a slight correlation with the corresponding MGFA, QMG, and MG-ADL in patients with thymoma.

DISCUSSION

In the Chinese AChR-MG population, the Changes in the AChR-Ab concentration in individuals with AChR-MG did not consistently correlate with the severity of clinical symptoms.

Myasthenic crisis appearing after resection of intracardiac ectopic thymoma with superior vena cava syndrome

Background

We describe herein an extremely rare case of intracardiac ectopic thymoma—only two pure cases have been reported to date—associated with myasthenia gravis, an infrequent complication of ectopic thymoma.

Case presentation

A 71-year-old woman with superior vena cava syndrome was found to have a large mass mainly located in the right atrium. Tumor resection under cardiopulmonary bypass was performed. The pathological diagnosis was type AB ectopic thymoma. The postoperative course was complicated by progressive respiratory failure, and she was diagnosed with myasthenic crisis based on clinical signs and the edrophonium test. The patient recovered and was weaned from prolonged mechanical ventilation after receiving intravenous immunoglobulin, and was subsequently discharged uneventfully.

Conclusions

This is the first report of myasthenic crisis due to intracardiac ectopic thymoma. Residual thymoma is a risk factor for the development of post-thymectomy myasthenia gravis, and long-term follow-up is required.

Thymoma pathology and myasthenia gravis outcomes

INTRODUCTION

There is limited evidence regarding the impact of World Health Organization (WHO) subtype of thymoma on post-thymectomy outcome of thymoma-associated myasthenia gravis (TAMG). The objective was to determine if the pathological subtypes of thymoma were associated with post-thymectomy outcomes of myasthenia gravis (MG), in patients with TAMG.

METHODS

We performed a retrospective study of consecutive patients with TAMG who attended the neuromuscular clinic between January 2018 and December 2019 with a minimum follow-up of 1 y after thymectomy. Outcome measures were MG Impairment Index (MGII), single-simple question (SSQ), Myasthenia Gravis Foundation of America post-intervention status (MGFA PIS) and non-responder MG status at last assessment.

RESULTS

Ninety-five patients were included; mean age at onset was 48.1 ± 12.1 y; 54(56.8%) were females. Thirteen patients developed MG post-thymectomy. The most common thymoma was WHO type B2 in 39 (41.1%). Most patients (40, 42.1%) had Masaoka stage II thymoma. There was no association of thymoma subtypes or Masaoka stage of disease with age, gender, MG phenotype, serology, post-thymectomy onset, interval from onset to thymectomy, MGII, SSQ, MGFA PIS, or non-responder status. Associations were found between positive serology and lower MGII (11.1 ± 14.2 vs 23 ± 12.9, P = .050), thymic follicular hyperplasia (TFH) and higher SSQ (89.3 ± 11.7 vs 80.1 ± 20.2, P-.043), and lack of recurrence and higher SSQ (84.1 ± 18 vs 72.5 ± 20, P = .037).

DISCUSSION

The WHO pathological subtype of thymoma did not correlate with MG outcomes. However, positive acetylcholine antibody serology, presence of TFH, and non-recurrence of thymoma predict a favorable outcome.

Risk factors for developing post-thymectomy myasthenia gravis in patients with thymoma

BACKGROUND

Thymectomy is required for the treatment of thymoma-associated myasthenia gravis (MG). However, MG may develop only after thymectomy, a condition known as post-thymectomy MG. This study aimed to investigate the risk factors for post-thymectomy MG in patients with thymoma.

METHODS

We retrospectively identified 235 patients with thymoma who underwent thymectomy at a single hospital from January 2008 to December 2017: 44 with preoperatively diagnosed MG were excluded, leaving 191 patients in the final analysis. Univariable survival analyses using Cox proportional hazards regression model and Kaplan-Meier estimate were conducted to identify risk factors for post-thymectomy MG.

RESULTS

Post-thymectomy MG developed in 4.2% (8/191) of the patients with thymoma between 18 days and 108 mo after surgery. Hazard ratios (HRs) of pre- and postoperative anti-acetylcholine receptor antibody (AChR-Ab) titers were 2.267 (P = .002) and 1.506 (P < .001), respectively. Patients with extended thymectomy had a low chance of post-thymectomy MG (HR 0.035, P = .007). Larger thymoma (HR, 1.359; P = .005) and type A or AB thymoma according to World Health Organization histological classification (HR, 11.92; P = .021) were associated with higher chances of post-thymectomy MG. Within the subgroup of preoperatively AChR-Ab seropositive patients, post-thymectomy MG developed in 22.2% (6/27).

CONCLUSIONS

Pre- and postoperative AChR-Ab levels should be measured in patients with thymoma. A large thymoma and partial thymectomy appear to be associated with a higher probability of post-thymectomy MG.

Report of a case of necrotizing autoimmune myopathy with thymoma-associated myasthenia gravis

Purpose: Myasthenia gravis (MG) is an autoimmune disease and closely related to thymoma. Inflammatory myopathy may accompany with other autoimmune diseases. However, concurrence of inflammatory myopathy and MG is very rare. Necrotizing autoimmune myopathy (NAM), a rare form of inflammatory myopathy, is characterized by necrosis and regeneration of myocytes in proximal muscles without significant inflammation. The aim of the study was to report a rare case of NAM and concomitant thymoma-associated MG after thymectomy.Materials and methods/results: A 27-year-old female patient presented with muscle soreness and weakness in four limbs. Eyelid fatigue and neostigmine tests were negative, and no ptosis was found but the electromyographic examination (EMG) showed myogenic damage and a gradual decrease in the amplitude (20%) of EMG activities evoked by repetitive electrical stimulation. Antibodies against AChR and increased titer of creatine kinase were detected and plaque-like signals in both legs were found in magnetic resonance imaging. Myositis-related antibodies were negative but necrotic myocytes without inflammatory cell infiltration, and MHC-1 positive muscle fibers were found in muscle biopsy. Pathological examination confirmed anterior mediastinal B2 type thymoma. Five weeks after thymectomy, she started to show typical MG symptoms. No recurrence of thymoma was found but immunoassay showed a higher titer of AChR-Ab. Myositis-related antibodies negative necrotizing autoimmune myopathy (NAM) was reported to be associated with thymoma-associated MG.Conclusions: The patient showed symptoms related NAM but developed MG-related symptoms only after thymectomy. The mechanisms for the phenomena may be related to immune dysfunction associated with thymoma.

High Neutrophil Count as a Negative Prognostic Factor for Relapse in Patients with Thymic Epithelial Tumor

PURPOSE

Preoperative neutrophil count is reportedly associated with poor prognosis in cancer patients. This study aimed to investigate the clinical significance of pre-treatment peripheral blood cell counts in patients with thymic epithelial tumors (TETs).

METHODS

A retrospective review of 71 patients with completely resected TETs [64 thymoma, 6 thymic carcinoma, and 1 thymic neuroendocrine tumor] between 2000 and 2018 was conducted. Associations between tumor recurrence and pre-treatment peripheral blood cell counts of leukocytes (WBC), neutrophils (Neut), lymphocytes (Lymph), monocytes (Mono), and platelets (Plt) were analyzed. Optimal cut-off points were selected using receiver operating characteristic curve analysis to predict tumor recurrence.

RESULTS

High WBC (≥ 7000), Neut (≥ 4450), and Plt (≥ 226 × 10³) counts had significantly poor relapse-free survival (RFS), but high Lymph (≥ 1950) and Mono (≥ 400) did not. High Neut had the strongest correlation with recurrence (area under curve, 0.800); we focused on the analysis between high-Neut and low-Neut groups. High Neut count significantly correlated with smoking history, pre-treatment C-reactive protein level, and advanced stage; high Neut count and aggressive histology tended to show correlations. RFS was significantly poorer in the high-Neut group than in the low-Neut group (p = 0.003), with 5-year RFS rates of 63.8% and 96.8%, respectively. High Neut count was a significant adverse predictor for RFS and cumulative incidence of recurrence (p = 0.005 and p < 0.001, respectively). The risk scoring system comprising high Neut count, advanced stage, and aggressive histology demonstrated better prognostic ability than any prognostic factors alone.

CONCLUSIONS

High Neut count significantly correlated with TET recurrence, suggesting a negative prognostic effect of latent inflammation in TET patients.

Risk Factors for the Exacerbation of Myasthenic Symptoms After Surgical Therapy for Myasthenia Gravis and Thymoma

Extended thymectomy is employed for patients with myasthenia gravis (MG) and/or thymoma with elevated serum antiacetylcholine receptor antibody (AchR) titers. However, MG symptoms occasionally worsen in post-thymectomy patients. We explored the risk factors for exacerbation of MG symptoms after surgical therapy for patients with MG and/or thymoma with an elevated AchR titer. We retrospectively analyzed 90 patients suffering from MG and/or thymoma with an elevated AchR titer who underwent thymectomy in our institute. Patients were classified into Improved, Unchanged, and Exacerbated groups by assessing their postoperative myasthenic symptoms, amount of medication, and incidence of myasthenic crisis. Risk factors for postoperative exacerbation of myasthenic symptoms were assessed by comparing the Exacerbated with the Improved and Unchanged groups. Of the 90 patients, 29 were classified into the Improved group, 47 into the Unchanged group, and 14 into the Exacerbated group. The presence of thymoma and Masaoka stage were significantly different between the Exacerbated and Improved/Unchanged groups. Although preoperative AchR titers did not significantly differ among the groups, the perioperative AchR titers in the Exacerbated group were significantly higher than those in the other groups (P = 0.003). A multiple logistic regression analysis with stepwise forward selection showed that advanced-stage thymoma was a risk factor for postoperative exacerbation of myasthenic symptoms (P = 0.007). Patients with advanced-stage thymoma have a relative risk for exacerbation of myasthenic symptoms after surgical therapy.

Tumor location may affect the clinicopathological features and prognosis of thymomas

BACKGROUND

The current staging systems do not consider the tumor location of thymomas, and its clinical relevance is poorly understood. This study aimed to evaluate the impact of tumor location on the clinicopathological features and prognosis of thymomas.

METHODS

We performed a retrospective review of patients at our institution who underwent an extended thymectomy for a thymoma from 1976 to 2015. The tumor location was classified as either the superior or inferior mediastinum based on the maximum tumor diameter. The clinicopathological characteristics of the thymoma were also evaluated. Kaplan-Meier estimates and Cox proportional hazards models were used to analyze the survival outcomes and risk factors for recurrence.

RESULTS

A total of 194 patients with thymoma were eligible for this study. Compared with the inferior mediastinum group (n = 167), the superior mediastinum group (n = 27) had a higher frequency of myasthenia gravis (MG), advanced Masaoka-Koga staging, disease progression and recurrence (P < 0.05). The Kaplan-Meier analysis demonstrated thymomas in the superior mediastinum had worse survival outcomes that included overall survival, progression-free survival and disease-free survival (P < 0.05). The multivariate analysis showed tumor location was an independent prognostic factor for all the survival outcomes (P < 0.05). Furthermore, the tumor location (P = 0.004) and Masaoka-Koga stage (P < 0.001) were the only two independent risk factors for recurrence in the multivariate analysis.

CONCLUSIONS

The clinicopathological features of thymomas on MG, Masaoka-Koga staging, disease progression, and recurrence were different between locations of superior and inferior mediastinum locations. Thymomas in the superior mediastinum tended to be associated with worse survival and increased recurrence.

Frequency and features of myasthenia gravis developing after thymectomy

BACKGROUND AND PURPOSE

Thymectomy is an effective treatment for myasthenia gravis (MG) with anti-acetylcholine receptor (AChR) antibodies. We rarely encounter patients who develop MG after surgery for thymic tumors. This study aimed to investigate the characteristics and frequency of post-thymectomy onset (PostTx) MG.

METHODS

We reviewed the clinical information of thymoma-associated MG in 158 patients. Of these, 18 (11%) patients with PostTx MG were identified.

RESULTS

The presence of anti-AChR antibodies (82%) and electrophysiological abnormalities (50%) was confirmed before thymectomy in patients with PostTx MG. The clinical characteristics of PostTx MG were similar to those of pre-thymectomy onset (PreTx) MG. In PostTx MG, the duration between thymectomy and MG onset were distributed as < 6 months (early-onset PostTx MG) and ≥ 6 months (late-onset PostTx MG). Notably, some patients with late-onset PostTx MG were associated with thymoma relapse.

CONCLUSION

Our results suggest that approximately 11% of patients with thymoma-associated MG were PostTx MG and pre-surgical assessment of anti-AChR antibody titer or electrophysiological testing may predict PostTx MG development. However, no difference in clinical manifestation and prognosis was observed between PreTx MG and PostTx MG.

Myasthenia gravis appearing after thymectomy heralding recurrent thymoma

INTRODUCTION

Thirty to fifty percent of thymoma patients develop myasthenia gravis (MG). In 1.5-28% of cases, MG appears many years after removal of a thymoma.

PATIENTS AND METHODS

We present a case report of a 72-year-old female who presented with MG four months after total thymectomy.

RESULTS

A 72-year-old female patient presents with MG four months after total thymectomy. Imaging revealed a PET-positive nodule anterior to the superior vena cava. By median sternotomy, the nodule was removed at our hospital. Pathology confirmed a recurrent B2/B3 thymoma with R0 resection. No adjuvant therapy was given. Large population studies show the appearance of new-onset MG associated with recurrent thymoma in 3% of cases.

CONCLUSIONS

New-onset MG postthymectomy heralds recurrent disease in 3% of cases. Thorough screening is needed in such patients.

The Cancer Genome Atlas dataset-based analysis of aberrantly expressed genes by GeneAnalytics in thymoma associated myasthenia gravis: focusing on T cells

Background

Myasthenia gravis (MG) is a group of autoimmune disease which could be accompanied by thymoma. Many differences have been observed between thymoma-associated MG (TAMG) and non-MG thymoma (NMG). However, the molecular difference between them remained unknown. This study aimed to explore the differentially expressed genes (DEGs) between the two categories and to elucidate the possible pathogenesis of TAMG further.

Methods

DEGs were calculated using the RNA-Sequencing data from 11 TAMG and 10 NMG in The Cancer Genome Atlas (TCGA) database. GeneAnalytics was performed to characterize the associations between DEGs and tissues and cells, diseases, gene ontology (GO) terms, pathways, phenotypes, and drug/compounds, respectively. Genes related to T cells were sorted out using LifeMapDiscovery Cells and Tissues Database. Genes directly related to the phenotype of autoimmune diseases that were identified by VarElect were validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

Results

The expression level of 169 genes showed a significant difference between the two groups, with 94 up-regulated and 75 down-regulated. Overexpression of six genes (ATM, SFTPB, ANKRD55, BTLA, CCR7, TNFRSF25), which are expressed in T cells and directly related to autoimmune disease through VarElect, was identified. The overexpression of soluble BTLA (sBTLA) (P=0.027), CCR7 (P=0.0018), TNFRSF25 (P=0.0013) and ANKRD55 (P=0.0026) was validated by RT-qPCR in thymoma tissues from our center.

Conclusions

Overexpression of sBTLA, CCR7, TNFRSF25 and ANKRD55 was identified and validated by RT-qPCR, which could partly explain the underlying pathogenesis in TAMG.

Thymolipoma-associated Myasthenia Gravis with High Titer of Anti-MuSKAb: A Case Report

Myasthenia gravis (MG) is a neuromuscular junction disorder caused by pathogenic autoantibodies to some parts of the post-synaptic muscle endplates. About 85% of generalized MG patients have autoantibodies against post-synaptic acetyl-choline receptors (AChR). From the 10-15% of the remaining patients, 45-50% are positive for Muscle Specific Tyrosine Kinase-Antibody (MuSK-Ab). It is believed that the thymus has a critical role in the pathogenesis of the disease with AChR-Ab, specially in patients with thymic abnormalities. In contrast, the role of thymus gland in MG with anti-MuSK-Ab is not clearly obvious. Patients with this antibody virtually have normal or only minimal follicular hyperplastic thymus. The presence of anti-MuSK Ab in a thymolipomatous (an uncommon tumor of thymus) MG is an atypical and new finding of MG because of not only thymolipoma but the presence of anti-MuSK antibodies which makes this case different from the previous reports of the antibodies-associated MG. Here, we present a young woman with thymolipoma and MG (a very uncommon kind of tumor-associated MG) and high level of anti-MuSK-Ab.

[Clinical Study on the Prognosis of Patients with Thymoma with Myasthenia Gravis]

背景与目的

胸腺瘤常伴发重症肌无力（myasthenia gravis, MG），但是这些患者行胸腺切除的预后与MG的关系尚不明确。本研究旨在探讨影响胸腺瘤合并MG患者预后的因素。

方法

回顾性分析中国胸腺瘤协作组（Chinese Alliance for Research of Thymoma, ChART）数据库1992年-2012年875例随访20年资料完整的胸腺瘤病例，分析世界卫生组织（World Health Organization, WHO）组织学分型、Masaoka分期、术后辅助治疗与MG及预后的关系。

结果

胸腺瘤WHO组织学分型与MG有相关性，差异有统计学意义（χ²=24.908, P < 0.001）。MG发生率为22.7%，其中B2型（58/178, 32.58%） > B3型（65/239, 27.20%） > B1型（27/132, 20.45%） > AB型（43/267, 16.10%） > A型（6/59, 10.17%），Masaoka分期与MG无相关性（χ²=1.365, P=0.714）。生存分析表明WHO分型、Masaoka分期与预后有关（P < 0.05），而是否合并MG（χ²=0.113, P=0.736）、是否行胸腺扩大切除（χ²=1.548, P=0.213）、术后辅助放疗（χ²=0.380, P=0.538）与预后无相关，术后辅助化疗与差的预后相关（χ²=14.417, P < 0.001）。是否行胸腺扩大切除与MG的疗效有相关性（χ²=24.695, P < 0.001）。

结论

胸腺瘤患者是否合并MG和是否行胸腺扩大切除与预后无相关性，胸腺扩大切除可改善MG患者的疗效。

Giant thymoma successfully resected via median sternotomy and anterolateral thoracotomy: a case report

Background

Some patients with thymoma present with a very large mass in the thoracic cavity. Although the most effective treatment for thymoma is surgical resection, it is difficult to perform because of the size of the tumor and the infiltration of tumor into the surrounding organs and vessels. We report a patient with a giant thymoma that was completely resected via a median sternotomy and left anterolateral thoracotomy.

Case presentation

A 63-year-old woman presented with a mass in the left thoracic cavity that was incidentally found on a chest X-ray. Chest computed tomography revealed a giant mass (16 × 10 cm) touching the chest wall and diaphragm and pressed against the heart and left upper pulmonary lobe. Complete resection was performed via a median sternotomy and left anterolateral thoracotomy. The tumor was histologically diagnosed as a WHO type B2 thymoma, Masaoka stage II.

Conclusions

Giant thymomas tend to grow expansively without invasion into surrounding organs and vessels. Surgical resection that employs an adequate approach must be considered, regardless of the size of the tumor.

Onset and Evolution of Clinically Apparent Myasthenia Gravis After Resection of Non-myasthenic Thymomas

Patients with thymoma and without clinical or electromyographical myasthenic signs may occasionally develop myasthenia several years after thymectomy. Hereby, we investigated the predictors and the evolution of this peculiar disease. We performed a retrospective analysis in 104 consecutive patients who underwent thymectomy between 1987 and 2013 for thymoma without clinical or electromyographic signs of myasthenia gravis. Predictors of post-thymectomy onset of myasthenia gravis were investigated with univariate time-to-disease analysis. Evolution of myasthenia was analyzed with time-to-regression analysis. Eight patients developed late myasthenia gravis after a median period of 33 months from thymectomy. No significant correlation was found for age, gender, Masaoka's stage, and World Health Organization histology. Only high preoperative serum acetylcholine-receptor antibodies titer (>0.3 nmol/L) was significantly associated with post-thymectomy myasthenia gravis at univariate time-to-disease (P = 0.003) analysis. Positron emission tomography was always performed in high-titer patients, and increased metabolic activity was detected in 4 of these patients. Surgical treatment through redo-sternotomy or video-assisted thoracoscopy was performed in these last cases with a remission in all patients after 12, 24, 32 and 48 months, respectively. No patient under medical treatment has yet developed a complete remission. In our study the presence of preoperative high-level serum acetylcholine receptor antibodies was the only factor significantly associated with the development of post-thymectomy myasthenia gravis. The persistence of residual islet of ectopic thymic tissue was one of the causes of the onset of myasthenia and its surgical removal was successful.

Could thymomectomy be a reasonable option for non-myasthenic thymoma patients?

Background

Complete resection is the mainstay of treatment for thymoma, but few studies have investigated the extent of resection on normal thymus. Extended thymectomy is considered the treatment of choice for myasthenic patients with thymoma, while the optimal therapy for non-myasthenic patients is still a matter of debate. The aim of this retrospective study was to compare extended thymectomy vs. thymomectomy in non-myasthenic thymoma patients for (I) oncological outcome, (II) multicentric thymoma occurrence and (III) postoperative myasthenia gravis (MG) development.

Methods

A retrospective comparative study was conducted on 92 non-myasthenic patients with completely resected thymoma, according to the extent of resection: extended thymectomy (70 patients) vs. R0-mediastinal thymomectomy (22 patients). Clinical and pathological characteristics, oncological outcome and postoperative MG occurrence were compared between the two study groups.

Results

We did not observe any significant differences in gender, age, symptomology, preoperative chemotherapy, histology, tumour size, adjuvant therapy or complications. There were no recorded postoperative mortalities. Stage distribution was different between the two groups: similar percentages of early stage thymoma for both groups were present, but there was a prevalence of stage III for extended thymectomy and stage IV for thymomectomy (P<0.01). At a median follow-up of 77.4 months (range 1-255 months), no statistically significant differences were recorded in local recurrence (P=0.396), thymoma related deaths (P=0.504), multicentric thymoma occurrence (P=0.742) and postoperative MG development (P=0.343). A high preoperative anti-acetylcholine receptor antibodies (ARAb) serum titer assay was statistically correlated with postoperative MG occurrence (r=0.49, P<0.05).

Conclusions

Thymomectomy appears to be a valid treatment option for non-myasthenic thymoma patients, as this procedure was associated to the same 5-year oncological results, compared to extended thymectomy, for both stage I-II small thymomas and patients with giant unilateral masses, as well as advanced diseases. Moreover, thymomectomy was not associated to an increased rate of postoperative MG.

Temporal deterioration of neurological symptoms and increase of serum acetylcholine receptor antibody levels after thymectomy: a case report of a cat with myasthenia gravis

Neurological signs and serum acetylcholine receptor antibody (AChR-Ab) levels before and after thymectomy were monitored in a 6-year-old male cat with acquired Myasthenia Gravis (MG) as a paraneoplastic syndrome of thymoma. Soon after surgery, the neurological symptoms relapsed, and the cholinesterase inhibitor was administered to control them. The AChR-Ab levels increased postoperatively until 90 days after surgery. This is the first report on long term measurements of serum AChR-Ab levels in a cat with MG. Although thymectomy is valuable for the removal of thymoma, it may not resolve MG symptoms, neurological signs and serum AChR-Ab levels, without medication early after surgery. Also, this case report indicates that the AChR-Ab level might be a guide to detect a deterioration of MG symptoms.

[Thymectomy versus Tumor Resection for Early-stage Thymic Malignancies: A Chinese Alliance for Research in Thymomas (ChART) Retrospective Database Analysis]

背景与目的

探采用中国胸腺肿瘤协作组胸腺肿瘤多中心回顾性数据库，探讨胸腺切除范围对早期胸腺上皮肿瘤预后的影响。

方法

选择Masaoka-Koga分期Ⅰ期、Ⅱ期且术前没有接受新辅助治疗的患者，根据术中胸腺切除程度，分为胸腺切除组及胸腺瘤切除组。对比分析两组患者的临床特点及预后差异。

结果

共有1, 047例患者纳入研究，其中胸腺切除组入组796例患者、胸腺瘤切除组入组251例患者。对于术前合并重症肌无力（myasthenia gravis, MG）的患者，胸腺切除组术后的MG的缓解率明显优于胸腺瘤切除组（91.6% vs 50.0%, P < 0.001）。胸腺切除组的10年总体生存率（overall survival, OS）为90.9%，胸腺瘤切除组的10年OS为89.4%，两者之间没有统计学差异（P=0.732）。胸腺切除组术后复发率为3.7%，胸腺瘤切除组术后复发率为6.2%，两组之间无统计学差异（P=0.149）。进一步分层分析显示，对于Masaoka-Koga Ⅰ期患者，胸腺切除组和胸腺瘤切除组在复发率上没有差异（3.2% vs 1.4%, P=0.259）；然而在Masaoka-Koga Ⅱ期患者中，胸腺切除组的复发率明显低于胸腺瘤切除组的复发率（2.9% vs 14.5%, P=0.001）。

结论

胸腺切除是治疗胸腺上皮肿瘤的标准手术方式，特别是对于Masaoka-Koga Ⅱ期及合并MG的患者。

Thymectomy versus tumor resection for early-stage thymic malignancies: a Chinese Alliance for Research in Thymomas retrospective database analysis

BACKGROUND

To evaluate the surgical outcomes of tumor resection with or without total thymectomy for thymic epithelial tumors (TETs) using the Chinese Alliance for Research in Thymomas (ChART) retrospective database.

METHODS

Patients without preoperative therapy, who underwent surgery for early-stage (Masaoka-Koga stage I and II) tumors, were enrolled for the study. They were divided into thymectomy and thymomectomy groups according to the resection extent of the thymus. Demographic and surgical outcomes were compared between the two patients groups.

RESULTS

A total of 1,047 patients were enrolled, with 796 cases in the thymectomy group and 251 cases in the thymomectomy group. Improvement rate of myasthenia gravis (MG) was higher after thymectomy than after thymomectomy (91.6% vs. 50.0%, P<0.001). Ten-year overall survival was similar between the two groups (90.9% after thymectomy and 89.4% after thymomectomy, P=0.732). Overall, recurrence rate was 3.1% after thymectomy and 5.4% after thymomectomy, with no significant difference between the two groups (P=0.149). Stratified analysis revealed no significant difference in recurrence rates in Masaoka-Koga stage I tumors (3.2% vs. 1.4%, P=0.259). However in patients with Masaoka-Koga stage II tumors, recurrence was significantly less after thymectomy group than after thymomectomy (2.9% vs. 14.5%, P=0.001).

CONCLUSIONS

Thymectomy, instead of tumor resection alone, should still be recommended as the surgical standard for thymic malignancies, especially for stage II tumors and those with concomitant MG.

Clinical features of patients with Myasthenia gravis from the Henan province, China

INTRODUCTION

Myasthenia gravis (MG) occurs globally, and many studies have indicated that there are regional differences in epidemiology, biomarkers, and prognosis of MG.

METHODS

A total of 478 patients with MG who visited hospitals in the Henan Province between January 2010 and February 2014 were included. Age, gender, age at onset, serum antibody, thymus pathology, treatment information, and Myasthenia Gravis Foundation of America (MGFA) classification were assessed.

RESULTS

Compared with previous reports from other areas, we found some differences in MG patients from Henan. The proportion of childhood MG in our study was lower than other reports of Oriental patients with MG. There seems to be an association between onset age, muscle involvement, and acetylcholine receptor antibody levels. Thymectomy improved the symptoms in 78.5% of thymectomy-treated patients.

CONCLUSIONS

These differences are likely related to geographical, environmental, and ethnic differences. Understanding these differences will help us to define more specific treatment.

Stage-based treatment for thymoma in due consideration of thymectomy: a single-center experience and comparison with the literature

Background

Thymomas represent an uncommon and heterogeneous group of intrathoracic malignancies which require different treatments corresponding to their individual tumor stage. The objective of this study was to review the efficacy of our applied stage-based treatment for thymoma in due consideration of thymectomy.

Methods

This is a single-center, institutional review board-approved retrospective study of 50 consecutive patients with thymoma treated at our division within 10 years.

Results

There were 29 women (58 %) and 21 men (42 %), mean age 58.3 years. Twenty nine (58 %) had clinical symptoms and 14 (28 %) had myasthenia gravis. Forty-five patients (90 %) underwent thymectomy and complete resection was done in 42 cases (93.3 %). Histologic results were 6 subtype A, 5 AB, 8 B1, 12 B2, 12 B3, and 7 C. The Masaoka staging system revealed 20 stage I, 18 stage II, 6 stage III, and 6 stage IV. Two patients had neoadjuvant therapy and 25 received postoperative treatment. Five (11.1 %) had tumor recurrence, treated with re-resection. The 5-year disease-free survival was 91.5 %. Two patients died of tumor progression and three died of other causes (10 %). The 5-year overall survival was 82.3 % and the median survival time was 92.1 months. The 5-year survival rate after thymectomy was 87.2 % and the median survival was 92.1 months.

Conclusions

Complete resection still remains the mainstay in the treatment of non-metastatic thymoma and should be performed whenever feasible. Close multidisciplinary teamwork is mandatory to optimize the neurologic outcome and to prolong postoperative survival.

Risk Factors and Outcomes in Cats with Acquired Myasthenia Gravis (2001-2012)

Background

Acquired myasthenia gravis (MG) in cats most commonly causes generalized weakness without megaesophagus and is more often associated with a cranial mediastinal mass, compared to dogs.

Hypothesis/Objectives

To extend the clinical findings described in the report of 2000 on MG in cats (J Am Vet Med Assoc 215:55–57).

Animals

Two hundred and thirty‐five cats with MG.

Methods

Retrospective case study to evaluate the long‐term outcome and incidence of spontaneous remission in myasthenic cats. Information including signalment, clinical presentation, presence of and type of cranial mediastinal mass, treatment including surgical versus medical, survival time, and outcome including spontaneous remissions was collected and analyzed in cats diagnosed at the Comparative Neuromuscular Laboratory, University of California San Diego by detection of acetylcholine receptor antibody titers >0.3 nmol/L by immunoprecipitation radioimmunosassay.

Results

Acquired MG in cats is associated with a euthanasia rate of 58%. Abyssinian and Somali cats had an increased incidence of MG compared to mixed breed cats or cats of other breeds. A cranial mediastinal mass, most commonly thymoma, was observed in 52% of the cats, which is higher than in the previous report. Spontaneous remission is not a characteristic of MG in cats.

Conclusions and clinical importance

Myasthenia gravis in cats is a chronic disease associated with a high incidence of a cranial mediastinal mass. Spontaneous remission is not common and clinicians should warn owners of the necessity for long‐term treatment. The clinical outcome with a cranial mediastinal mass did not differ between surgical or medical treatment.

Ectopic cervical thymoma accompanied by Good's syndrome

Ectopic cervical thymoma (ECT) is a rare tumor that is frequently misdiagnosed as a thyroid tumor or other malignancy. A 34-year-old male with a right palpable neck mass had been mistakenly diagnosed with T-cell lymphoblastic lymphoma even after an open biopsy. The atypical clinical course, including hypogammaglobulinemia, led us to the correct diagnosis; ECT accompanied by Good's syndrome (GS). After the intravenous infusion of gammaglobulin, tumor resection and a subsequent video-assisted thoracoscopic extended thymectomy were performed. The final diagnosis was type AB thymoma, Masaoka stage I. This report is, to the best of our knowledge, the first description of this extremely rare combination.

Thymus, thymoma and myasthenia gravis

Myasthenia gravis is an autoimmune disease. An autoantibody directed toward acetylcholine receptor (AChR) causes the destruction of the postsynaptic membrane and a reduction of the number of AChRs at neuromuscular junctions. A very puzzling, but interesting characteristic of myasthenia gravis is that many of the patients have an abnormality in their thymus. Many have a hyperplastic thymus with germinal centers, while others have a thymic tumor. How is the abnormality of the thymus related to myasthenia gravis? This review will summarize the existing evidence and try to find the missing link between the thymus and myasthenia gravis. The review will also comment on two distinct populations of myasthenia gravis patients without thymoma. The autoimmunity found in elderly patients is nonspecific and initiated via a different mechanism from the initiation of myasthenia gravis in younger patients.

Post-thymectomy myasthenia gravis with an episode of Osserman stage III

Here, we present the first case of post-thymectomy Myasthenia Gravis with onset at Osserman stage III. An 81-year-old woman was admitted for an abnormal shadow seen in a chest radiograph. She had no symptoms of Myasthenia Gravis. Acetylcholine receptor antibody was within the normal range. Chest computed tomography (CT) showed a bulky anterior mediastinal tumor. She was diagnosed as having thymoma by tissue biopsy under CT guidance. The tumor was completely resected by performing thymothymectomy, left upper lobectomy, pericardial resection, and phrenicectomy. Pathological examination of the tumor identified it as a thymoma (type B2, Masaoka stage II). Two months after the surgery, she experienced the onset of post-thymectomy myasthenia gravis with Osserman stage III. The acetylcholine receptor antibody level was remarkably elevated (220 nmol/L); however, there was no evidence of tumor recurrence.

Published guidelines for management of thymoma

Guidelines for treatment of thymoma are prevalent in US literature, and many have been published by organizations in the United Kingdom, Canada, and Japan. This article reviews these many guidelines and summarizes them for the reader.