Type B thymomas in patients with myasthenia gravis display a distinctive pattern of αß TCR and IL-7 receptor α expression on CD4+CD8+ thymocytes.

Thymoma is closely associated with myasthenia gravis (MG). However, due to the heterogeneity of thymoma and the intricate pathogenesis of MG, it remains unclear why some patients with thymoma develop MG and others do not. In this study, we conducted a comparative phenotype analysis of thymocytes in type B thymomas in patients with MG (MG (+) thymomas) and without MG (MG (-) thymomas) via fluorescence-activated cell sorting (FACS). Our results show that the developmental stages defined by the expression of CD3, CD4, and CD8 were largely maintained in both MG (+) and MG (-) thymomas, with CD4+CD8+ cells constituting the majority of thymocytes in type B thymoma, and no significant difference between this cell population was observed in MG (+) and MG (-) thymomas.We discovered that CD4+CD8+ thymocytes in MG (+) thymomas expressed low levels of αß TCR and high levels of IL-7 receptor α (IL-7Rα), whereas in MG (-) thymomas, CD4+CD8+ thymocytes exhibited the opposite pattern of αß TCR and IL-7Rα expression. These results suggest that the positive and negative selection processes of CD4+CD8+ thymocytes might differ between MG (+) thymomas and MG (-) thymomas. The expression of the Helios transcription factor is induced during negative selection and marks a group of T cells that have undergone negative selection and are likely to be deleted due to strong TCR binding with self-peptides/MHC ligands. We observed that the percentage of Helios-positive CD4SP T cells was greater in MG (-) than in MG (+) thymomas. Thus, the differentially regulated selection process of CD4+CD8+ thymocytes, which involves TCR and IL-7/IL-7Rα signaling, is associated with the presence of MG in type B thymomas.

Thymic gene expression analysis reveals a potential link between HIF-1A and Th17/Treg imbalance in thymoma associated myasthenia gravis.

Myasthenia gravis (MG) is an immune-mediated disease frequently associated with thymic changes. Increased T helper 17 (Th17) cell activity and dysfunctional regulatory T (Treg) cells have been demonstrated in subgroups of MG. On the other hand, hypoxia-inducible factor 1 (HIF-1) has been shown to regulate the Th17/Treg balance by inducing Th17 differentiation while attenuating Treg development. To identify the underlying mechanisms of different thymic pathologies in MG development, we evaluated thymic samples from thymoma-associated myasthenia gravis (TAMG), MG with hyperplasia (TFH-MG) and thymoma without MG (TOMA) patients. Differential gene expression analysis revealed that TAMG and TFH-MG cells are associated with different functional pathways. A higher RORC/FOXP3 ratio provided evidence for Th17/Treg imbalance in TAMG potentially related to increased HIF1A. The hypoxic microenvironment in thymoma may be a driver of TAMG by increasing HIF1A. These findings may lead to new therapeutic approaches targeting HIF1A in the development of TAMG.

[Thymoma with Partial Anomalous Pulmonary Venous Drainage from the Left Upper Lobe:Report of a Case].

A 73-year-old woman presented with left anterior chest pain and back pain. Computed tomography (CT) scan showed an anterior mediastinal tumor. It also showed partial anomalous pulmonary venous drainage (left superior pulmonary vein draining into the left brachiocephalic vein), and the tumor was located near the left brachiocephalic vein. The operation was performed through a median sternotomy to resect the thymus and tumor with partial resection of the left upper lobe due to the tumor's adhesion to the left upper lobe. One of the vascular anomalies encountered in adult thoracic surgery is partial anomalous pulmonary venous drainage. It is important to recognize the presence of such an anomaly on imaging and to anticipate the surgical procedure with a preoperative surgical technique.

Postoperative radiotherapy does not improve survival in patients with Masaoka-Koga stage IIB thymomas: A propensity score matching study based on the SEER database.

This study, based on a population, explored the prognostic value of postoperative radiotherapy (PORT) for Masaoka-Koga IIB stage thymomas. Patients diagnosed with thymoma from 2004 to 2017 in the Surveillance, Epidemiology, and End Results (SEER) database were included in the retrospective study. Through propensity score matching, the baseline characteristics of the patients were successfully matched to mitigate the selection bias of PORT. Survival rates and survival curves were compared between the PORT and non-PORT groups, with potential confounding factors addressed using a multivariate Cox regression model. In this study, 785 cases of IIB stage thymoma were included from the SEER database, and 303 patients were successfully matched between PORT and non-PORT groups through propensity score matching, with no significant differences in baseline characteristics. In the PORT and non-PORT groups, 10-year overall survival rates were 65.2% versus 59.6%, and cancer-specific survival rates were 87.0% vs. 84.4%, PORT did not yield statistically significant improvements in overall survival (P = .275) or cancer-specific survival (P = .336) for stage IIB thymomas. Based on the SEER database, the results of our study indicated that PORT does not confer a significant survival benefit for IIB stage thymomas.

Our experience with robotic-assisted thymic surgery.

Thoracic surgery is increasingly influenced by the development of minimally invasive approaches which have also influenced surgery in the area of the anterior mediastinum. The previously standard approach to the thymus via partial sternotomy was gradually replaced by the videothoracoscopic approach in most cases. In recent years, robotically assisted surgery has been gaining ground worldwide in this area, as well. The aim of our paper is to provide a comprehensive overview of procedures in the field of the thymus, including their indications, and to share our first experience with robot-assisted thymus surgery. At the 3rd Department of Surgery, since the start of the robot-assisted thymus surgery program, 23 thymectomies have been performed using this approach, of which 17 were performed for thymoma, 3 for myasthenia gravis, and 3 for parathyroid adenoma localized in thymus tissue. From our experience and the available data, it follows that the length of hospitalization, the rate of complications and the resulting effect of robot-assisted procedures is comparable to VTS procedures; however, the robot-assisted surgery also allows for mini-invasive treatment even in significantly obese patients and in patients with advanced thymic tumors who would otherwise be indicated for open thymectomy.

Thymic carcinoma presenting with overlap polyarthritis and myositis: A rare paraneoplastic syndrome in childhood.

Thymic tumors are very rare neoplasms in children and account for less than 1% of mediastinal tumors in pediatric patients. One-third of the pediatric patients present with symptoms related to the compression of the tumor mass on the surrounding anatomic structures, and paraneoplastic syndromes such as myasthenia gravis, pure red cell aplasia, acquired hypogammaglobulinemia, and connective tissue disorders, which rarely occur in children with thymic tumors. Herein, we report a case of thymic carcinoma mimicking the symptoms of a connective tissue disease with symmetrical polyarthritis accompanying myositis, fever, weight loss, and malaise in a 15-year-old male patient. To our knowledge, this is the first case pediatric thymic carcinoma accompany with severe polyarthritis and myopathy, thus we have reviewed the current literature regarding the cases of thymic malignancies coexisting with paraneoplastic syndromes in children.

Absence of ATM leads to altered NK cell function in mice.

Ataxia-telangiectasia (A-T) is a rare disorder caused by genetic defects of A-T mutated (ATM) kinase, a key regulator of stress response, and characterized by neurodegeneration, immunodeficiency, and high incidence of cancer. Here we investigated NK cells in a mouse model of A-T (Atm-/-) showing that they are strongly impaired at killing tumor cells due to a block of early signaling events. On the other hand, in Atm-/- littermates with thymic lymphoma NK cell cytotoxicity is enhanced as compared with ATM-proficient mice, possibly via tumor-produced TNF-α. Results also suggest that expansion of exhausted NKG2D+ NK cells in Atm-/- mice is driven by low-level expression of stress-inducible NKG2D ligands, whereas development of thymoma expressing the high-affinity MULT1 ligand is associated with NKG2D down-regulation on NK cells. These results expand our understanding of immunodeficiency in A-T and encourage exploring NK cell biology in A-T patients in the attempt to identify cancer predictive biomarkers and novel therapeutic targets.

Thymic Imaging Pitfalls and Strategies for Optimized Diagnosis.

Thymic imaging is challenging because the imaging appearance of a variety of benign and malignant thymic conditions are similar. CT is the most commonly used modality for mediastinal imaging, while MRI and fluorine 18 fluorodeoxyglucose (FDG) PET/CT are helpful when they are tailored to the correct indication. Each of these imaging modalities has limitations and technical pitfalls that may lead to an incorrect diagnosis and mismanagement. CT may not be sufficient for the characterization of cystic thymic processes and differentiation between thymic hyperplasia and thymic tumors. MRI can be used to overcome these limitations but is subject to other potential pitfalls such as an equivocal decrease in signal intensity at chemical shift imaging, size limitations, unusual signal intensity for cysts, subtraction artifacts, pseudonodularity on T2-weighted MR images, early imaging misinterpretation, flow and spatial resolution issues hampering assessment of local invasion, and the overlap of apparent diffusion coefficients between malignant and benign thymic entities. FDG PET/CT is not routinely indicated due to some overlap in FDG uptake between thymomas and benign thymic processes. However, it is useful for staging and follow-up of aggressive tumors (eg, thymic carcinoma), particularly for detection of occult metastatic disease. Pitfalls in imaging after treatment of thymic malignancies relate to technical challenges such as postthymectomy sternotomy streak metal artifacts, differentiation of postsurgical thymic bed changes from tumor recurrence, or human error with typical "blind spots" for identification of metastatic disease. Understanding these pitfalls enables appropriate selection of imaging modalities, improves diagnostic accuracy, and guides patient treatment. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Autoimmunity in thymic epithelial tumors: a not yet clarified pathologic paradigm associated with several unmet clinical needs.

Thymic epithelial tumors (TETs) are rare mediastinal cancers originating from the thymus, classified in two main histotypes: thymoma and thymic carcinoma (TC). TETs affect a primary lymphoid organ playing a critical role in keeping T-cell homeostasis and ensuring an adequate immunological tolerance against "self". In particular, thymomas and not TC are frequently associated with autoimmune diseases (ADs), with Myasthenia Gravis being the most common AD present in 30% of patients with thymoma. This comorbidity, in addition to negatively affecting the quality and duration of patients' life, reduces the spectrum of the available therapeutic options. Indeed, the presence of autoimmunity represents an exclusion criteria for the administration of the newest immunotherapeutic treatments with checkpoint inhibitors. The pathophysiological correlation between TETs and autoimmunity remains a mystery. Several studies have demonstrated the presence of a residual and active thymopoiesis in adult patients affected by thymomas, especially in mixed and lymphocytic-rich thymomas, currently known as type AB and B thymomas. The aim of this review is to provide the state of art in regard to the histological features of the different TET histotype, to the role of the different immune cells infiltrating tumor microenvironments and their impact in the break of central immunologic thymic tolerance in thymomas. We discuss here both cellular and molecular immunologic mechanisms inducing the onset of autoimmunity in TETs, limiting the portfolio of therapeutic strategies against TETs and greatly impacting the prognosis of associated autoimmune diseases.

Taste disorders and alopecia in myasthenia gravis.

BACKGROUND: Non-motor symptoms in myasthenia gravis (MG) are rarely confirmed. Although there are some small cohort studies, a large-systemic survey has not yet been performed. METHODS: We investigated the incidence and clinical characteristics of patients with MG who had taste disorders and alopecia using data of 1710 patients with MG enrolled in the Japan MG Registry 2021. RESULTS: Among them, 104 (6.1%) out of 1692 patients and 138 (8.2%) out of 1688 patients had histories of taste disorders and alopecia, respectively. Among the patients with MG, taste disorders were significantly more common in women, those with severe symptoms, refractory MG, or thymoma-associated MG, and were less common in those with ocular MG. The taste disorders often occurred after the onset of MG and often responded to MG treatments. Alopecia was more common in MG patients with a history of bulbar palsy and thymoma, and it often occurred before the onset of MG and sometimes responded to MG treatments. Multivariate logistic regression analysis revealed taste disturbance was associated with worst quantitative MG score and thymoma-associated MG; and alopecia was associated with thymoma-associated MG. CONCLUSION: Clinicians should be aware of the non-motor symptoms in MG, especially in patients with severe myasthenic symptoms and thymoma-associated MG.

A basaloid carcinoma with multilocular thymic cyst mimicking a mediastinal teratoma.

This case report details a rare thymic basaloid carcinoma initially misinterpreted as a mediastinal teratoma, underscoring the diagnostic challenges posed by such tumors. A 71-year-old female presented with an asymptomatic anterior mediastinal tumor discovered incidentally during a routine health examination. Surgical intervention, followed by pathological and immunohistochemical analysis including CK-pan, p63, p40, and CD117 molecules, led to a definitive diagnosis of basaloid carcinoma of the thymus. This case highlights the critical importance of differential diagnosis in mediastinal lesions, especially those presenting with multilocular thymic cysts on chest CT. The subxiphoid video-assisted thoracoscopic surgery enabled complete tumor resection with minimal trauma and favorable postoperative outcomes. The patient opted against further radiotherapy or chemotherapy and she has survived for over eight months without recurrence. This case report contributes to the growing understanding of thymic basaloid carcinoma, a rare and potentially aggressive thymic carcinoma subtype. It emphasizes the necessity for precise surgical techniques and enhanced diagnostic acumen among cardiothoracic surgeons and oncologists.

Making an accurate diagnosis of anterior mediastinal lesions: a proposal for a new diagnostic algorithm from the BTOG Thymic Malignancies Special Interest Group.

Due to the rising demand in cross-sectional thoracic imaging, anterior mediastinal lesions are being identified with increasing frequency. Following iterative and multidisciplinary discussions, the BTOG Thymic Malignancies Special Interest Group have developed an algorithm to standardise the diagnostic approach for these relatively uncommon but important conditions which span from benign (thymic remnant, thymic hyperplasia and thymic cysts) to suspected localised thymomas to suspected more aggressive malignancy (thymic carcinoma, lymphoma and germ cell tumours). For each condition, we provide a brief description, an overview of the key radiological findings and a description of the proposed algorithm including the rationale behind the recommendations. We also highlight the role of magnetic resonance (MR) imaging for the characterisation of anterior mediastinal masses in specific indications when the necessary local resources and expertise exist. In addition, we hope this provides the rationale for service development in MR of the anterior mediastinum where current resource and expertise requires development. Through this standardised pathway, we hope to drive improvements in patient care by rationalising surveillance schedules, avoiding unnecessary resections of benign entities with their associated morbidity and optimising the diagnostic work-up prior to the appropriate treatment of anterior mediastinal malignancies.

Analysis of 25 surgical cases of thymic neuroendocrine tumors and thymic carcinoma.

BACKGROUND: The purpose of this study was to evaluate the clinicopathological characteristics of patients who underwent surgical resection for thymic neuroendocrine tumors (TNET) or thymic carcinoma. METHODS: In this study, we retrospectively evaluated the clinicopathological characteristics of our surgical patients at Fukuoka University Hospital from January 1995 to December 2018. RESULTS: There were nine cases of TNET and 16 cases of thymic carcinoma. Regarding the pathological type, the TNET group included three atypical carcinoid cases, two large cell neuroendocrine tumor cases, two small cell carcinoma cases, and two other cases. The thymic carcinoma group included 15 squamous carcinoma cases and one case of adenosquamous carcinoma. Based on the Masaoka-Koga staging system, six TNET cases and 11 thymic carcinoma cases were stage III or IV. The complete resection rate was 77% in the TNET group and 81% in the thymic carcinoma group. Additional chemotherapy and/or radiotherapy was performed in five cases of TNET and 11 cases of thymic carcinoma. The five-year survival rate and five-year disease-free survival rate were 87.5% and 75.0% in the TNET group and 58.9% and 57.1% in the thymic carcinoma group, respectively, with no significant difference between the two groups (P = 0.248 and P = 0.894, respectively). In the univariate analysis, complete resection was a statistically significant prognostic factor (P = 0.017). CONCLUSION: In this study, no difference in prognosis was observed between TNET and thymic carcinomas. To understand the characteristics of these tumors, further case accumulation and multicenter clinical studies are needed. (243words).

Is Minimally Invasive Resection of Large Thymoma Appropriate?

BACKGROUND: Current practice patterns suggest open rather than minimally invasive (MIS) approaches for thymomas >4 cm. We hypothesized there would be similar perioperative outcomes and overall survival between open and MIS approaches for large (>4 cm) thymoma resection. METHODS: The National Cancer Database was queried for patients who underwent thymectomy from 2010 to 2020. Surgical approach was characterized as either open or MIS. The primary outcome was overall survival and secondary outcomes were margin status, and length of stay (LOS). Differences between approach cohorts were compared after a 1:1 propensity match. RESULTS: Among 4121 thymectomies, 2474 (60%) were open and 1647 (40%) were MIS. Patients undergoing MIS were older, had fewer comorbidities, and had smaller tumors (median; 4.6 vs 6 cm, P < .001). In the unmatched cohort, MIS and open had similar 90-day mortality (1.1% vs 1.8%, P = .158) and rate of positive margin (25.1% vs 27.9%, P = .109). MIS thymectomy was associated with shorter LOS (2 (1-4) vs 4 (3-6) days, P < .001). Propensity matching reduced the bias between the groups. In this cohort, overall survival was similar between the groups by log-rank test (P = .462) and multivariate cox hazard analysis (HR .882, P = .472). Multivariable regression showed shorter LOS with MIS approach (Coef -1.139, P < .001), and similar odds of positive margin (OR 1.130, P = .150). DISCUSSION: MIS has equivalent oncologic benefit to open resection for large thymomas, but is associated with shorter LOS. When clinically appropriate, MIS thymectomy may be considered a safe alternative to open resection for large thymomas.

Long-term follow-up and exploratory analysis of lenvatinib in patients with metastatic or recurrent thymic carcinoma: Results from the multicenter, phase 2 REMORA trial.

OBJECTIVES: The main objective of this report was to detail the long-term follow-up data from the REMORA study, which investigated the safety and efficacy of lenvatinib in patients with thymic carcinoma. In addition, an exploratory analysis of the association between relative dose intensity (RDI) and the efficacy of lenvatinib is presented. MATERIALS AND METHODS: The single-arm, open-label, phase 2 REMORA study was conducted at eight Japanese institutions. Forty-two patients received oral lenvatinib 24 mg once daily in 4-week cycles until the occurrence of intolerable adverse events or disease progression. The REMORA long-term follow-up data were evaluated, including overall survival (OS). RDI was calculated by dividing the actual dose administered to the patient by the standard recommended dose. This trial is registered on JMACCT (JMA-IIA00285) and on UMIN-CTR (UMIN000026777). RESULTS: The updated median OS was 28.3 months (95 % confidence interval [CI]: 17.1-34.0 months), and the OS rate at 36 months was 35.7 % (95 % CI: 21.7 %-49.9 %). When grouped by RDI of lenvatinib, the median OS was 38.5 months (95 % CI: 31.2-not estimable) in patients with ≥ 75 % RDI and 17.3 months (95 % CI: 13.4-26.2 months) in patients with < 75 % RDI (hazard ratio 0.46 [95 % CI: 0.22-0.98]; P = 0.0406) at 8 weeks. Patients who maintained their lenvatinib dose over 8 weeks had a higher objective response rate than patients whose doses were reduced (75.0 % vs 29.4 %; P = 0.0379). No new safety concerns or treatment-related deaths were reported, and lenvatinib had a tolerable safety profile. CONCLUSION: This follow-up report updated OS in patients with metastatic or recurrent thymic carcinoma. A higher RDI of lenvatinib at 8 weeks could be associated with improved outcomes.

Postoperative radiotherapy results in 192 epithelial thymic tumours patients with 10 years of follow-up.

PURPOSE: To assess the prognostic factors and patterns of failure of patients consecutively treated with surgery and postoperative radiation therapy (PORT) for thymic epithelial tumours (TET). PATIENTS AND METHODS: Data from 192 TET patients who were operated and received PORT at a single centre from 1990 to 2019 was retrospectively analysed. RESULTS: Most patients had thymoma (77 %, B247%), were classified Masaoka-Koga stage III (35 %) or IV (32 %) and had a R0 (75 %) resection. Radiotherapy was delivered at a median dose of 50.4 Gy (range, 42-66 Gy; ≥ 60 Gy in 17 %), 63 (33 %) patients were treated by intensity-modulated radiation therapy and elective nodal radiotherapy was used for 37 %. At a median follow-up of 10.9 years, the 10-year overall survival (OS) and progression-free survival (PFS) rates were 62 % (95 % CI: 54-70 %) and 47 % (95 % CI: 39-55 %), respectively. Locoregional recurrence (LRR) occurred in 72/192 (38 %) patients, distributed as 6 local, 45 regional and 21 both local and regional. LRR were mainly located to the pleura: 66/72 (92 %) and 16/72 (22 %; 16/192 in total, 8 %) were in-field. Distant relapse (DR) were observed in 30 patients (16 %), resulting in 10-year locoregional (LRC) and distant control rates of 58 % (95 % CI: 50-66 %) and 82 % (95 % CI: 77-88 %), respectively. In the multivariate analysis, Masaoka-Koga stage (HR [hazard ratio]: 1.9; p = 0.001), thymic carcinomas/neuroendocrine tumours (TC) (HR: 1.6; p = 0.045) and ECOG PS > 1 (HR: 1.9; p = 0.02) correlated with poorer OS. Higher Masaoka-Koga stage (HR: 2.6; p < 0.001) associated with a decreased LRC but not R1 status (HR: 1.2; p = 0.5) or WHO histology classification. TC (HR: 3.4; p < 0.001) and a younger age (HR: 2.5; p = 0.02) correlated with DR. CONCLUSION: Approximately one-third of the TET in our study experienced a LRR, mainly to the pleura, and 8% in total were in-field. The place of radiotherapy should be better defined in higher risk thymoma patients within prospective randomized studies.