Myasthenia gravis as a prognostic marker in patients with thymoma

Hide-and-Seek With Spindle-Cell-Component-Poor Metaplastic Thymoma

Metaplastic thymoma is a rare biphasic thymic tumor with indolent behavior and recurrent YAP1::MAML2 gene rearrangement. Although the diagnosis of this tumor is usually straightforward based on hematoxylin and eosin (H&E) findings alone, cases with scant spindle-cell ("pseudosarcomatous stroma") components can be easily confused with more commonly occurring type A thymoma. We present a case of metaplastic thymoma with a sparse stroma-like spindle-cell component, discussing its histological and immunohistochemical hints and drawing attention to the visual similarity to type A thymoma. This is also the first published case of metaplastic thymoma with associated psoriasis.

Development and characterization of agonistic antibodies targeting the Ig-like 1 domain of MuSK

Muscle-specific kinase (MuSK) is crucial for acetylcholine receptor (AChR) clustering and thereby neuromuscular junction (NMJ) function. NMJ dysfunction is a hallmark of several neuromuscular diseases, including MuSK myasthenia gravis. Aiming to restore NMJ function, we generated several agonist monoclonal antibodies targeting the MuSK Ig-like 1 domain. These activated MuSK and induced AChR clustering in cultured myotubes. The most potent agonists partially rescued myasthenic effects of MuSK myasthenia gravis patient IgG autoantibodies in vitro. In an IgG4 passive transfer MuSK myasthenia model in NOD/SCID mice, MuSK agonists caused accelerated weight loss and no rescue of myasthenic features. The MuSK Ig-like 1 domain agonists unexpectedly caused sudden death in a large proportion of male C57BL/6 mice (but not female or NOD/SCID mice), likely caused by a urologic syndrome. In conclusion, these agonists rescued pathogenic effects in myasthenia models in vitro, but not in vivo. The sudden death in male mice of one of the tested mouse strains revealed an unexpected and unexplained role for MuSK outside skeletal muscle, thereby hampering further (pre-) clinical development of these clones. Future research should investigate whether other Ig-like 1 domain MuSK antibodies, binding different epitopes, do hold a safe therapeutic promise.

Comparison of Short-Term Post-Thymectomy Outcomes by Time-Weighted Dosages of Drug Requirements between Thymoma and Non-Thymoma Myasthenia Gravis Patients

(1) Background: Early thymectomy is suggested in all clinically indicated myasthenia gravis (MG) patients. However, short-term clinical response after thymectomy in MG patients has been limitedly described in the literature. This study aimed to compare the 5-year post-thymectomy outcomes between thymoma (Th) and non-thymoma (non-Th) MG patients. (2) Methods: MG patients aged ≥18 years who underwent transsternal thymectomy and had tissue histopathology reports in Songklanagarind Hospital between 2002 and 2020 were enrolled in a retrospective review. The differences in the baseline demographics and clinical characteristics between ThMG and non-Th MG patients were studied. We compared the time-weighted averages (TWAs) of daily required dosages of pyridostigmine, prednisolone or azathioprine to efficiently maintain daily living activities and earnings between the MG patient groups during 5 consecutive years following thymectomy. Post-thymectomy clinical status, exacerbations or crises were followed. Descriptive statistics were used for analysis with statistical significance set at p < 0.05. (3) Results: ThMG patients had significantly older ages of onset and shorter times from the MG diagnosis to thymectomy. Male gender was the only significant factor associated with ThMG. TWAs of the daily MG treatment drug dosages required showed no differences between the groups. Additionally, the rates of exacerbations and crises were not different, but decremental trends were shown in both groups after the thymectomies. (4) Conclusions: The daily dosage requirements of MG treatment drugs were not different. There was a trend of decreasing adverse event rates despite no statistically significant differences during the first 5 years after thymectomy in ThMG and non-ThMG patients.

Thymoma and Myasthenia Gravis: An Examination of a Paraneoplastic Manifestation

Thymoma is a rare type of malignancy but is considered one of the most common neoplasms that occur in the anterior mediastinum. A large proportion of thymomas are associated with paraneoplastic syndromes, such as myasthenia gravis. Whenever feasible, the standard of care for the treatment of thymoma should focus on the control of paraneoplastic syndromes, surgical resection, and adjuvant therapy if appropriate. A 36-year-old female patient with a significant past medical history of obesity and iron deficiency anemia who underwenten bloc resection of thymoma three months prior now presented to the benign hematology clinic to establish care for the management of anemia. Upon review of systems, the patient incidentally reported fatigue, weakness with repetitive motion, occasional blurred vision, headaches, and exertional dyspnea. Physical examination was positive for horizontal nystagmus. Given the patient's history and clinical findings, suspicion of myasthenia gravis was high. Further work-up demonstrated anti-acetylcholine receptor titers of 5.70 nmol/L (normal < 0.21 nmol/L), supporting a diagnosis of myasthenia gravis in this patient. She was subsequently started on pyridostigmine. Often, patients with thymoma experience paraneoplastic syndrome-related symptoms prior to thymectomy, and in many cases thymectomy is curative. However, in the case presented, we examine a patient that was asymptomatic prior to surgery and subsequently reported the onset of symptoms following what we suspect was an exacerbation due to general anesthesia and pain control medications. We argue that all patients with thymoma should undergo systematic evaluation and treatment of paraneoplastic syndromes, regardless of clinical symptoms and prior to surgery, in order to improve patient quality of life and hospital outcomes.

Oncological resection, myasthenia gravis and staging as prognostic factors in thymic tumours: a Chilean case series

Background

Thymic epithelial tumours are rare and highly heterogeneous. Reports from the United States suggest an overall incidence of 0.15 per 100,000/year. In contrast, the incidence of these tumours in Latin America is largely unknown and reports are scarce, somewhat limited to case reports.

Methods

Herein, we report a series of 38 thymic tumours from a single institution, retrospectively incorporated into this study. Patient characteristics and outcomes including age, sex, stage, paraneoplastic syndromes, treatment regimens and the date of decease were obtained from medical records.

Results

Most cases in our series were females and young age (<50 years old) and early stage by Masaoka-Koga or the Moran staging systems. Also, a 34% of patients had myasthenia gravis (MG). Next, we analysed overall survival rates in our series and found that the quality of surgery (R0, R1 or R2), MG status and staging (Masaoka-Koga, Moran or TNM) were prognostic factors. Finally, we compared our data to larger thymic tumour series.

Conclusions

Overall, our study confirms complete surgical resection as the standard, most effective treatment for thymic epithelial tumours. Also, the Masaoka-Koga staging system remains as a reliable prognostic factor but also the Moran staging system should be considered for thymomas.

Thymomatous myasthenia gravis: 10-year experience of a single center

OBJECTIVES

To summarize the clinical features of thymomatous myasthenia gravis (T-MG), examine the association between MG and thymoma, and identify the related factors or predictors for long-term prognosis of T-MG.

METHODS

A retrospective, observational study was conducted on 100 patients with T-MG and 96 patients with non-T-MG (NT-MG) between January 1, 2009 and December 31, 2019. The baseline characteristics were recorded for each patient. Logistic regression was used to measure the association between all clinical variables and T-MG prognosis.

RESULTS

Between the T-MG and NT-MG groups, age at onset (45.66 ± 11.53 years vs 39.06 ± 14.39 years); age >40 years (72.0% vs. 40.6%); AChR-Ab positive rate (100.0% vs. 83.3%); Myasthenia Gravis Foundation of America (MGFA) classification at the worst condition (≥grade III, 61.0% vs. 33.0%); thyroid dysfunction (7.0% vs. 20.8%); and outcome (complete stable remission + pharmacologic remission + improvement, 74.0% vs. 93.7%) were statistically significant (P < .05). Presence of thymoma (OR = 0.196, 95%CI = 0.076-0.511, P = .001) was a risk factor for MG. Male sex, post-operative complications, higher grade of MGFA classification, and thymoma Masaoka-Koga pathological stage were risk predictors for long-term prognosis of T-MG (P < .1). Use of preoperative anticholinesterase drugs (OR = 5.504, 95%CI = 1.424-21.284, P = .013) was identified as an independent predictor for T-MG.

CONCLUSION

T-MG is clinically different from NT-MG, and thymoma is considered a risk factor for MG. Preoperative anticholinesterase drug use is a protective factor for long-term prognosis of T-MG. A comprehensive understanding of the characteristics of T-MG will likely help improve its prognosis.

Myasthenia Gravis Is Not an Independent Prognostic Factor of Thymoma: Results of a Propensity Score Matching Trial of 470 Patients

Objective

The association between the prognosis of thymoma and MG remains controversial. Differences in clinical characteristics and treatments between patients with and without MG may affect the findings of those studies. We designed this propensity score matching trial to investigate whether MG is an independent prognostic predictor in thymoma.

Methods

Patients with pathologically diagnosed thymoma and MG were enrolled in the MG group. Moreover, the propensity score matching method was used to select patients who were diagnosed with thymoma without MG from the database of two participating centers. Matched factors included sex, age, Masaoka stage, pathological subtypes, and treatments. Matched patients were enrolled in the non-MG group. Chi-squared test was used to compare the characteristics of the two groups. Overall survival, local-regional relapse-free survival, distant metastasis-free survival, progression-free survival, and cancer-specific survival were calculated from the diagnosis of thymoma using the Kaplan–Meier method.

Results

Between April 1992 and October 2018, 235 patients each were enrolled in the MG and non-MG groups (1:1 ratio). The median ages of patients in the MG and non-MG groups were 46 years old. The World Health Organization pathological subtypes were well balanced between the two groups (B2 + B3: MG vs. non-MG group, 63.0 vs. 63.4%, p = 0.924). Most patients in both groups had Masaoka stages I–III (MG vs. non-MG group, 90.2 vs. 91.5%, p = 0.631). R0 resections were performed in 86.8 and 90.2% of the MG and non-MG groups, respectively (p = 0.247). The median follow-up time of the two groups was 70.00 months (MG vs. non-MG group, 73.63 months vs. 68.00 months). Five-year overall survivals were 92.5 and 90.3%, 8-year overall survivals were 84.2 and 84.2%, and 10-year overall survivals were 80.2 and 81.4% (p = 0.632) in the MG and non-MG groups, respectively. No differences were found in the progression-free survival, distant metastasis-free survival, and local-regional relapse-free survival between the two groups.

Conclusion

MG is not an independent or direct prognostic factor of thymoma, although it might be helpful in diagnosis thymoma at an early stage, leading indirectly to better prognosis.

Role of thymus on prognosis of myasthenia gravis in Turkish population

OBJECTIVE:

Myasthenia gravis (MG) is an autoimmune disease that may cause a disorder in transmission at the neuromuscular junction. Antibodies directed against acetylcholine receptors are responsible. The thymus is the place that that production of these antibodies mainly occurs. The thymus gland abnormalities and abnormal production of these antibodies are associated with MG. Consequently, thymectomy is a common treatment for MG. The nature of the disease makes it difficult to plan prospective, controlled trials; therefore, there is no current consensus among clinicians on a single algorithm of treatment, and the approach is frequently based on the observations and experiences of experts. The contributions to the literature largely consist of retrospective studies examining an approach to treatment and the effects of thymectomy on prognosis. In this retrospective study, evaluation of Turkish patients with myasthenia gravis was carried out for the importance of thymectomy and effects on prognosis.

METHODS:

In this study, 93 patients with myasthenia gravis whose followed up at Neuromuscular outpatient clinic between 1998–2018 were evaluated retrospectively. Type of disease, antibody status, treatment, thymectomy, thymus pathology and prognosis were assessed.

RESULTS:

Thymectomy had been a positive effect on the prognosis of the disease independent of the duration of disease and thymic pathology. The best results had been obtained with early thymectomy with short disease duration, younger age and patients with thymic hyperplasia. Success of therapy was limited with thymoma. With advanced age need for thymectomy was decreased.

CONCLUSION:

In the present study, evaluation of 93 patients with myasthenia gravis was done retrospectively and it was concluded that thymectomy had a positive effect on prognosis, especially in young patients when performed as early as possible. The most successful results were obtained in cases with thymic hyperplasia.