Thymic lipofibroadenoma of the anterior mediastinum: A rare case report

BACKGROUND

Lipofibroadenoma is an extremely rare thymic tumor, and the anterior mediastinum is the most common site.

CASE SUMMARY

A 21-year-old male was admitted with fever without obvious cause for 2 months. After admission, the patient's highest temperature was 38.3°C, accompanied by diarrhea. Physical examination showed coarse breath sounds in both lungs. Chest enhanced computed tomography (CT) showed a mass of mixed density shadow on the left side of the anterior mediastinum with a size of approximately 9.2 cm × 5 cm × 2.1 cm and a clear boundary mixed with a low fat density shadow. Mediastinal tumors were removed under general anesthesia by video-assisted thoracoscopic surgery. Macroscopically, a clear boundary was shown between the tumor and the remaining thymus. Microscopically, the tumor contained a large amount of mature adipose and fibrous tissue with scattered cord-like epithelial tissue and a small number of lymphocytes scattered in the stroma. The tumor lacked thymic bodies. The neoplastic epithelial cells were oval or polygonal and arranged in fissures, the nuclei were uniform in size and mild in shape, and mitosis was rare. Epithelial cells were positive for AE1/AE3 and CK19, lymphocytes were positive for CD3 and CD20, and fat and fibrous tissue were positive for S-100 and vimentin, respectively. The Ki67 labeling index was less than 5%. Based on histological features and immunophenotype, thymic lipofibroadenoma was diagnosed. The patient was followed up 1 year after the operation, and no recurrence or residual lesions were found on the X-ray re-examination.

CONCLUSION

Lipofibroadenoma is a benign thymic tumor, and thymectomy is regarded as the best treatment. The biological behavior of thymic lipofibroadenoma is good, and the recurrence rate is low.

Approach to Mediastinal Fine Needle Aspiration Cytology

Mediastinal fine needle aspirations are routinely encountered in cytopathology practice. Mediastinal lesions may pose diagnostic challenges owing to their rarity and locations associated with the complexity of the mediastinal anatomic structures in the thoracic cavity. Diagnosing mediastinal lesions and guiding patient management usually require correlating with clinical and radiologic findings, being familiar with cytomorphologic features and appropriately triaging the diagnostic material for ancillary testing. This review proposes a practical approach to interpret mediastinal fine needle aspirations and emphasizes potential diagnostic pitfalls for mediastinal lesions including benign cysts, thymic neoplasms, lymphoproliferative disorders, germ cell tumors, mesenchymal tumors, and metastatic tumors.

Prognostic factors for overall survival after surgical resection in patients with thymic epithelial tumors: A systematic review and meta-analysis

BACKGROUND

Thymic epithelial tumors (TETs) originate in the thymic epithelial cell, including thymoma and thymic carcinoma. Surgical resection is the first choice for most patients. However, some studies have shown that the factors affecting the prognosis of these patients are not consistent. To evaluate prognostic factors in patients with surgically resected thymic epithelial tumors, we performed a meta-analysis.

METHODS

We searched the Chinese biomedical literature database, Pubmed, Embase, Cochrane Library and other electronic databases. Studies including postoperative overall survival (OS) and predictors of TETs were included. We made a comprehensive analysis the hazard ratios (HRs) through a single proportional combination. HRs were combined using single proportion combinations.

RESULTS

The meta-analysis included 11,695 patients from 26 studies. The pooled OS was 84% at 5 years and 73% at 10 years after TETs operation. The age as continuous-year (HR 1.04, 95% confidence interval (CI) 1.02-1.04), incomplete resection (HR 4.41, 95% CI 3.32-5.85), WHO histologic classification (B2/B3 vs A/AB/B1 HR 2.76, 95% CI 1.25-6.21), Masaoka Stage (stage III/IV vs I/II HR 2.74, 95% CI 2.12-3.55,) were the poor prognostic factors.

CONCLUSIONS

For patients with TETs after surgical resection, advanced age, incomplete resection, WHO classification B2/B3, and higher Masaoka stage are risk factors for poor prognosis.

Unraveling the Immune Microenvironment of Thymic Epithelial Tumors: Implications for Autoimmunity and Treatment

Thymic Epithelial Tumors (TETs) represent a rare tumor family, originating from the epithelial component of the thymus gland. Clinicopathologically, they are segregated into six major subtypes, associated with distinct histological features and clinical outcomes. Their emergence and evolution are accompanied by the generation of a complex tumor microenvironment (TME), dominated by phenotypically and functionally divergent immune cellular subsets, in different maturation states and in analogies that vary significantly among different subtypes. These heterogenous leukocyte populations exert either immune-permissive and tumor-suppressive functions or vice versa, and the dynamic equilibrium established among them either dictates the tumor immune milieu towards an immune-tolerance state or enables the development of a productive spontaneous tumoricidal response. The immunologically “hot” microenvironment, defining a significant proportion of TETs, makes them a promising candidate for the implementation of immune checkpoint inhibitors (ICIs). A number of phase I and II clinical trials have already demonstrated significant, type-specific clinical efficacy of PD-L1 inhibitors, even though substantial limitations in their utilization derive from their immune-mediated adverse effects. Moreover, the completed clinical studies involved relatively restricted patient samples and an expansion in the enrolled cohorts is required, so that more trustworthy conclusions regarding the benefit from ICIs in TETs can be extracted.

Retrospective histopathology audit of thymectomy specimens: A clinicopathological study of 303 cases spanning the non-neoplastic, benign and malignant spectrum

AIMS

Thymectomy specimens are uncommon in routine histopathology practice. However, awareness of various pathologic entities and definite reporting of these specimens is paramount to optimal patient management. Our objective was to determine the histomorphologic spectrum of thymectomy specimens spanning the non-neoplastic, benign to malignant spectrum.

METHODS AND RESULTS

Thymectomies received over an 8-year period were retrospectively analyzed by reviewing clinical details and histologic findings in detail, incorporating the latest World Health Organization (WHO) 2015 histologic classification. A total of 303 thymectomy specimens (179 males/124 females, mean age 45.3 years [3-84 years]) were included. Around 51.2% (n = 155) patients had associated myasthenia gravis (MG), while 17.5% (n = 53) had incidentally detected anterior mediastinal mass (AMM). Non-neoplastic and benign pathologies comprised 31% (n = 94) cases and showed stronger association with MG (P = 0.009). Thymic follicular hyperplasia (TFH) was the commonest non-neoplastic pathology (n = 32), while the benign tumor group included thymic hemangioma/lymphangioma, thymolipoma, and ectopic parathyroid adenoma. Thymic epithelial tumors (TETs) comprised 64.7% cases, with majority being thymomas (185/303; 61.1%). Thymoma type B2 was the commonest histologic subtype and Stage I/T1 was the most frequent stage. Type A and AB thymomas affected older patients (P = 0.005) and were in lower stage (both Masaoka and American Joint Committee on Cancer [AJCC]) than type B thymomas (P = 0.007). No significant association between MG and thymoma subtype, patient sex or Masaoka stage was seen (P > 0.05). Thymic carcinomas comprised 11 cases and showed no association with MG (0/11, P < 0.001); squamous cell carcinoma was the commonest histologic type (8/11; 72.7%).

CONCLUSION

TETs are the commonest thymic lesions; however, a diverse spectrum of pathologic processes can affect the thymus.

Giant cell myositis associated with metastatic thymoma and granulomatous hypercalcaemia

Giant cell myositis (GCM) is a rare inflammatory myopathy associated with myasthenia gravis and thymoma. Here, we report on a woman in her late 50s with a history of myasthenia gravis, systemic lupus erythematosus and stage IV thymoma with pleural metastases, who presented with proximal weakness, neuromuscular respiratory failure and hypercalcaemia. She was diagnosed with GCM via muscle biopsy and screened for myocarditis but showed no evidence of myocardial involvement. Her hypercalcaemia was consistent with a granulomatous process, likely driven by her GCM. Her strength gradually improved, and her hypercalcaemia did not recur after treatment with high dose steroids, intravenous immune globulin and plasma exchange. Her course was complicated by several opportunistic infections in the setting of her immunosuppression. Despite the high morbidity associated with GCM, she demonstrated clinical improvement after initiating immunosuppressive therapy and continues to be managed in the outpatient setting.

The efficacy of 18F-FDG-PET-based radiomic and deep-learning features using a machine-learning approach to predict the pathological risk subtypes of thymic epithelial tumors

OBJECTIVE

To examine whether the machine-learning approach using 18-fludeoxyglucose positron emission tomography (18F-FDG-PET)-based radiomic and deep-learning features is useful for predicting the pathological risk subtypes of thymic epithelial tumors (TETs).

METHODS

This retrospective study included 79 TET [27 low-risk thymomas (types A, AB and B1), 31 high-risk thymomas (types B2 and B3) and 21 thymic carcinomas] patients who underwent pre-therapeutic 18F-FDG-PET/CT. High-risk TETs (high-risk thymomas and thymic carcinomas) were 52 patients. The 107 PET-based radiomic features, including SUV-related parameters [maximum SUV (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG)] and 1024 deep-learning features extracted from the convolutional neural network were used to predict the pathological risk subtypes of TETs using six different machine-learning algorithms. The area under the curves (AUCs) were calculated to compare the predictive performances.

RESULTS

SUV-related parameters yielded the following AUCs for predicting thymic carcinomas: SUVmax 0.713, MTV 0.442, and TLG 0.479 or high-risk TETs: SUVmax 0.673, MTV 0.533, and TLG 0.539. The best-performing algorithm was the logistic regression model for predicting thymic carcinomas (AUC 0.900, accuracy 81.0%), and the random forest (RF) model for high-risk TETs (AUC 0.744, accuracy 72.2%). The AUC was significantly higher in the logistic regression model than three SUV-related parameters for predicting thymic carcinomas, and in the RF model than MTV and TLG for predicting high-risk TETs (each; p < 0.05).

CONCLUSION

18F-FDG-PET-based radiomic analysis using a machine-learning approach may be useful for predicting the pathological risk subtypes of TETs.

ADVANCES IN KNOWLEDGE

Machine-learning approach using 18F-FDG-PET-based radiomic features has the potential to predict the pathological risk subtypes of TETs.

Thymoma exhibiting spontaneous regression with developing myasthenia gravis: A case report

Spontaneous regression (SR) of thymoma is rare. A 44-year-old man with right chest pain underwent computed tomography (CT), which showed an 11.0 cm mass in the anterior mediastinum and right pleural effusion. He refused surgery and was sent home without medication and additional treatment. One year later, the mass had regressed to 5.5 cm, and the right pleural effusion had disappeared. He was then lost to follow-up. Four years after the initial visit, he presented with diplopia and fatigue. A significant increase in his anti-acetylcholine receptor antibody levels led to myasthenia gravis (MG) diagnosis. CT revealed a regressed mediastinal mass (3.0 cm). After extended thymectomy, histologic analysis confirmed a thymoma type B2, Masaoka stage IIa. The SR was due to intratumoral infarction. This report is the first to describe MG developing during SR. Anterior mediastinal tumors undergoing SR should be differentiated from thymomas and MG perioperative development should be considered.

Thymic Carcinomas-A Concise Multidisciplinary Update on Recent Developments From the Thymic Carcinoma Working Group of the International Thymic Malignancy Interest Group

Thymic carcinomas are rare malignancies that in general arise in the prevascular (anterior) mediastinum. These tumors are usually invasive, often present at advanced stages, and typically behave aggressively. Studies are hampered by the paucity of these tumors, the large variety of carcinoma subtypes, and the lack of unique morphologic and immunophenotypic features. Despite these challenges, advances in diagnostic imaging, surgical approaches, systemic therapies, and radiation therapy techniques have been made. The WHO classification of thymic epithelial tumors has been updated in 2021, and the eighth tumor nodal metastasis staging by the American Joint Committee on Cancer/Union for International Cancer Control included thymic carcinomas in 2017. Molecular alterations that provide more insight into the pathogenesis of these tumors and that potentially permit use of novel targeted therapies are increasingly being identified. New approaches to radiation therapy, chemotherapy, and immunotherapy are under evaluation. International societies, including the International Thymic Malignancy Interest Group, European Society of Thoracic Surgeons, and Japanese, Chinese, and Korean thymic associations, have been critical in organizing and conducting multi-institutional clinical studies. Herein, we review contemporary multidisciplinary perspectives in diagnosis and management of thymic carcinoma.

Long Non-Coding RNAs in the Cell Fate Determination of Neoplastic Thymic Epithelial Cells

Thymic Epithelial Tumors (TETs) arise from epithelial cells of the thymus and are very rare neoplasms comprising Thymoma, Thymic carcinoma, and Thymic Neuroendocrine tumors that still require in-depth molecular characterization. Long non-coding RNAs (lncRNAs) are emerging as relevant gene expression modulators involved in the deregulation of several networks in almost all types of human cancer, including TETs. LncRNAs act at different control levels in the regulation of gene expression, from transcription to translation, and modulate several pathways relevant to cell fate determination under normal and pathological conditions. The activity of lncRNAs is strongly dependent on their expression, localization, and post-transcriptional modifications. Starting from our recently published studies, this review focuses on the involvement of lncRNAs in the acquisition of malignant traits by neoplastic thymic epithelial cells, and describes the possible use of these molecules as targets for the design of novel therapeutic approaches specific for TET. Furthermore, the involvement of lncRNAs in myasthenia gravis (MG)-related thymoma, which is still under investigation, is discussed.

COMPARATIVE ANALYSIS OF CURRENT SURGICAL APPROACHES TO THYMIC TUMORS TREATMENT

The aim of the work was a comparative analysis of scientific sources, covering current surgical approaches in the treatment of thymus tumors, as well as the analysis of the results of own experience in minimally invasive surgery for thymus neoplasm. Thymic hyperplasia include tumor-like disorders, cysts and thymic tumors, the latter compose for 60-90% of all thymic lesions. Over the past ten years, due to the development of technologies, a new trends of surgical treatment of thymic tumors has been proposed - minimally invasive techniques, which all over the world changes the historical dogmas concerning thymus surgery, since associated with shorter hospital stays, less intraoperative bleeding, the best aesthetic outcomes. There are four key problems are discussed in thymus surgery today: the role of minimally invasive surgery, the role of lymph node dissection, extension of resection in the case of nonmyasthenic thymoma, treatment of locally advanced tumors of the thymus with pleural defeats. A retro- and prospective analysis of the results of minimally invasive surgery was carried out in 18 patients with thymic tumors in our research, who received surgical therapy during 2018 and 2021 in the department of thoracic surgery (,,New Hospitals", Tbilisi, Georgia). The average age of patients was 51.4±13.2 (M±SD), 3 men (22.2%), 15 women (77.8%). All patients were performed thymectomy by videothoracoscopic method, there were no postoperative crises of myasthenia gravis and other complications in any case. Research results demonstrate high efficiency minimally invasive thymus surgery in clinic practice, which be of help to optimal management and allows to reduce the socio-economic loading on health service.

CT Radiomic Features for Predicting Resectability and TNM Staging in Thymic Epithelial Tumors

BACKGROUND

To explore the performance of a computed tomography based radiomics model in the preoperative prediction of resectability status and TNM staging in thymic epithelial tumors.

METHODS

We reviewed the last preoperative computed tomography scan of patients with thymic epithelial tumors prior to resection and pathology evaluation at our institution between February 2008 and June 2019. A total of 101 quantitative features were extracted and a radiomics model was trained using elastic net penalized logistic regressions for each aim. In the set-aside testing sets, discriminating performance of each model was assessed with area under receiver operating characteristic curve.

RESULTS

Our final population consisted of 243 patients with: 153 (87%) thymomas, 23 (9%) thymic carcinomas, and 9 (4%) thymic carcinoids. Incomplete resections (R1 or R2) occurred in 38 (16%) patients, and 67 (28%) patients had more advanced stage tumors (stage III or IV). In the set-aside testing sets, the radiomics model achieved good performance in preoperatively predicting incomplete resections (area under receiver operating characteristic curve: 0.80) and advanced stage tumors (area under receiver operating characteristic curve: 0.70).

CONCLUSIONS

Our computed tomography radiomics model achieved good performance to predict resectability status and staging in thymic epithelial tumors, suggesting a potential value for the evaluation of radiomic features in the preoperative prediction of surgical outcomes in thymic malignancies.

Management of severe hypertension due to lenvatinib in patients with advanced thymic carcinoma: A case report

RATIONALE

Thymic carcinoma (TC) is a malignant mediastinal tumor, and there are no established treatments for pre-treated patients with advanced TC. Recently, lenvatinib was approved for such patients in Japan, ahead of other countries. Higher dose lenvatinib may be more efficacious than conventional treatments, although many patients experience grade 3 hypertension. Therefore, lenvatinib dose reduction remains controversial in terms of efficacy and tolerability.

PATIENT CONCERNS

Case 1 involves a 72-year-old woman who underwent complete resection of TC and was taking cilnidipine and azilsartan for hypertension. Six years later, multiple lung metastases were observed, and lenvatinib was started. Case 2 involves a 60-year-old man with TC, and was taking amlodipine for hypertension. A chest computed tomography showed progression in primary and metastatic lesions, and the patient started lenvatinib.

DIAGNOSES

In both patients, grade 3 hypertension was observed after the administration of lenvatinib.

INTERVENTIONS

In Case 1, lenvatinib dose was reduced 3 times because lenvatinib was not interrupted despite grade 3 hypertension. In contrast, in Case 2, lenvatinib was interrupted when grade 3 hypertension occurred and was resumed after a decrease in blood pressure to baseline.

OUTCOMES

In Case 2, higher tumor regression may have been achieved because of the maintenance of a high dose of lenvatinib compared with that in Case 1.

LESSONS

Lenvatinib is a promising agent for advanced TC; however, hypertension should be addressed cautiously, especially at the outset of administration. Lenvatinib may have to be appropriately interrupted and resumed as soon as the blood pressure is controlled to maximize efficacy and minimize toxicity.

POU2F3 beyond thymic carcinomas: expression across the spectrum of thymomas hints to medullary differentiation in type A thymoma

The thymic medulla comprises various cell types, including tuft cells that are involved in innate immunity. We recently reported that in Western cohorts of patients, most thymic squamous cell carcinomas (TSQCCs), in contrast to thymomas, exhibit strong and extensive expression of tuft cell markers, including the tuft cell master regulator, POU2F3. On closer inspection of 94 thymomas that cover the full spectrum of thymoma histotypes, we now find by immunohistochemistry that approximately half of types A, AB, and B1 thymomas contain small numbers (< 10%) of cells expressing POU2F3, while most types B2 and B3 thymomas do not (p < 0.05). Further, in rarer types A and AB thymomas with adenoid growth pattern, POU2F3( +) cells formed aggregates and co-expressed KIT, as did the tumor cells in 100% (9/9) of TSQCCs expressing POU2F3. However, the expression of another tuft cell marker, L1CAM, still distinguished TSQCC from the spectrum of thymomas that were all L1CAM-negative. This study is the first to demonstrate the high frequency of POU2F3 expression in an Asian cohort of TSQCCs. The common occurrence of scattered POU2F3( +) cells in types A and AB thymomas hints at their variable degree of medullary differentiation and supports the historical hypothesis of the medullary nature of type A thymomas. Immunohistochemistry of L1CAM may be a valuable tool to differentiate TSQCCs from thymomas.

Computed tomography radiomics for the prediction of thymic epithelial tumor histology, TNM stage and myasthenia gravis

Objectives

To evaluate CT-derived radiomics for machine learning-based classification of thymic epithelial tumor (TET) stage (TNM classification), histology (WHO classification) and the presence of myasthenia gravis (MG).

Methods

Patients with histologically confirmed TET in the years 2000–2018 were retrospectively included, excluding patients with incompatible imaging or other tumors. CT scans were reformatted uniformly, gray values were normalized and discretized. Tumors were segmented manually; 15 scans were re-segmented after 2 weeks by two readers. 1316 radiomic features were calculated (pyRadiomics). Features with low intra-/inter-reader agreement (ICC<0.75) were excluded. Repeated nested cross-validation was used for feature selection (Boruta algorithm), model training, and evaluation (out-of-fold predictions). Shapley additive explanation (SHAP) values were calculated to assess feature importance.

Results

105 patients undergoing surgery for TET were identified. After applying exclusion criteria, 62 patients (28 female; mean age, 57±14 years; range, 22–82 years) with 34 low-risk TET (LRT; WHO types A/AB/B1), 28 high-risk TET (HRT; WHO B2/B3/C) in early stage (49, TNM stage I-II) or advanced stage (13, TNM III-IV) were included. 14(23%) of the patients had MG. 334(25%) features were excluded after intra-/inter-reader analysis. Discriminatory performance of the random forest classifiers was good for histology(AUC, 87.6%; 95% confidence interval, 76.3–94.3) and TNM stage(AUC, 83.8%; 95%CI, 66.9–93.4) but poor for the prediction of MG (AUC, 63.9%; 95%CI, 44.8–79.5).

Conclusions

CT-derived radiomic features may be a useful imaging biomarker for TET histology and TNM stage.

Synchronous Parathyroidectomy and Extended Thymectomy in Multiple Endocrine Neoplasia Type 1

A 49-year-old male was investigated for symptoms of hypercalcaemia which had been present for 3 months. An initial chest X-ray showed a large anterior mediastinal mass. Subsequent computed tomography (CT) scans also demonstrated a calcified lesion in the uncinate process of the pancreas, and a neck ultrasound showed parathyroid lesions. Given the combination of symptoms and tumours, this raised the possibility of multiple endocrine neoplasia type 1 (MEN-1) as the diagnosis. The lesions were later biopsy-proven atypical carcinoid neuroendocrine tumours. The patient underwent simultaneous neck dissection for bilateral subtotal parathyroidectomy and midline sternotomy for thymectomy of the large mediastinal mass.

Ectopic Cushing's syndrome due to thymic neuroendocrine tumours: a systematic review

Knowledge of ectopic Cushing's syndrome (CS) due to thymic neuroendocrine tumours (NETs) comes from short series or single cases. Our aim is to perform a systematic review using PubMed, Embase, Scopus, Ovid Medline and Biosis Previews of all cases with ectopic CS due to thymic NETs reported in the last 40 years and describe one illustrative patient attended in our institution. Search of literature: From 162 patients, 58.6% were male and mean age was 34.6 ± 13.9 years-old. Median of symptoms until diagnosis was 6 [2-24] months and 62% had aggressive CS. Imaging was positive in 93.7% (chest X-ray), 97.8% (computed tomography), 80.7% (somatostatin receptor scintigraphy) and median tumour size was 47 [25-68.5] mm. At presentation, 18% had localized disease, 26.2% locally invasive and 55.7% advanced. Eighty-eight present underwent surgery and histological subtypes were atypical (46.7%), typical (30.4%) and carcinoma (21.7%). Tumour persisted or recurred in 70.1%, 63% received radiotherapy and 45.2% chemotherapy. Follow-up median was 26.6 [14.5-57.5] months and mortality was reported in 35.8% with median survival of 38 [19-60] months. MEN-1 mutation was referred in 3.1%. Comparatively, carcinomas had aggressive CS more frequently while atypical showed advanced disease more often. In conclusion, thymic NETs causing ectopic CS are presented as aggressive hypercortisolism in the middle aged population. The disease is commonly extended at diagnosis and persists or recurs after surgery in most patients with a short term high mortality.

An unusual huge thymoma composed of sclerosing thymoma and type AB thymoma: A case report

RATIONALE

Sclerosing thymoma (ST) is quite a rare disease, as denoted in previous literature. Less than 20 cases of ST have been reported to date. However, the combined thymoma, composed of both type AB thymoma and ST, has never been described before.

PATIENT CONCERNS

The subject, a 49-year-old woman, came in with the chief complaint of cough for 10 days.

DIAGNOSES

Both the contrast-enhanced computed tomography scan and the ultrasonography showed a huge mass located in the right thoracic cavity with inhomogeneous contrast accompanied by the invasion of the pericardium and pleura. Subsequently, computed tomography-guided core-needle biopsy revealed type B2 thymoma, and type AB thymoma could not be excluded. Based on postsurgical histopathology and immunohistochemical finding, this tumor was given the final diagnosis of ST and type AB thymoma.

INTERVENTIONS

After 6 months of adjuvant chemotherapy and local radiotherapy, total thymectomy was performed.

OUTCOMES

The patient has been duly followed up for 1 year without any tumor recurrence.

LESSONS

ST is a very rare mediastinal neoplasm. Moreover, ST in combination with AB thymoma and affecting a large area, is unprecedented. Whether radiotherapy and chemotherapy have a certain effect on ST requires further investigation. In addition, due to the unclear recurrence rate of ST, long-term follow-up evaluation seems necessary.

Robotic thymectomy for thymomas: a retrospective follow-up study in the Netherlands

BACKGROUND

The Maastricht University Medical Center+ (MUMC+) is a Dutch center of expertise, appointed by the Netherlands Federation of University Medical Centres (NFU), for the treatment of thymomas. The aim of this study was to investigate the long-term oncological-, surgical-, and neurological outcomes of all patients who underwent a robotic thymectomy for a thymoma at the MUMC+.

METHODS

We retrospectively analyzed the clinical-pathological data of all consecutive patients with a thymoma who underwent robotic thymectomy using the DaVinci® Robotic System at the MUMC+ between April 2004 and December 2018. Follow-up data were collected from 60 referring Dutch hospitals.

RESULTS

In total, 398 robotic thymectomies were performed and 130 thymomas (32.7%) were found. Median follow-up time, procedure time and hospitalization were 46 months, 116 minutes and 3 days, respectively. In 8.4% of the patients a conversion was performed and in 20.8% a complication was registered. The majority of myasthenic patients with a thymoma went into remission, mostly within 12 to 24 months after thymectomy (81.0%). No statistical difference was found in the number of complications, conversions, incomplete resections or deaths between patients with myasthenia gravis and nonmyasthenic patients. Thirty-six patients (27.7%) underwent postoperative radiotherapy. The recurrence rate was 9.1% and the five-year thymoma-related survival rate was 96.6% .

CONCLUSIONS

Robotic thymectomy was found to be safe and feasible in early-stage thymomas, most advanced-stage thymomas and thymomatous myasthenia gravis. A national guideline could contribute to the improvement of the oncological follow-up of thymic epithelial tumors in the Netherlands.

T-Lymphoblastic Leukemia/Lymphoma and Thymoma: A Case Report and Review of the Literature of a Rare Association

The co-occurrence of thymoma and T-lymphoblastic lymphoma/leukemia is an extremely rare but previously reported association that poses a diagnostic and therapeutic challenge. We describe a 67-year-old patient with long-standing untreated B1 thymoma that presented with constitutional symptoms and a painless soft tissue mass on the right chest wall. Pathological analysis of the biopsy from the mass demonstrated T-lymphoblastic leukemia/lymphoma. The patient went through a complicated course, was refractory to several lines of therapy, and eventually underwent allogeneic hematopoietic stem cell transplantation in complete remission from a matched related donor. The association between thymoma and malignant neoplasms has been described in the literature, most notably with colorectal adenocarcinoma and thyroid cancer. Thymoma-associated leukemia is, however, extremely unusual, with limited reports in the literature. Distinguishing between thymoma and leukemia can be challenging and often requires meticulous diagnostic efforts. For patients with a past history of thymoma, awareness of this particular association should be bared in mind to allow earlier diagnosis and therapy.

Partial Versus Complete Thymectomy in Non-Myasthenic Patients With Thymoma: A Systematic Review and Meta-Analysis of Clinical Outcomes

The optimal extent of surgical resection for non-myasthenic patients with thymoma is controversial. The objective of this meta-analysis was to compare complete to partial thymectomy in non-myasthenic patients for oncological and postoperative clinical outcomes. We performed a PubMed and EMBASE search (from inception to January 2020) for English-language studies directly comparing partial to complete thymectomy for thymoma resection. Clinical endpoints studied included overall and disease-free survival, Masaoka and World Health Organization staging, adjuvant therapy, postoperative complications, postoperative drainage, length of hospital stay, thymoma-related deaths, postresection development of myasthenia gravis, incomplete resection, and recurrence. Random effects meta-analyses across all clinical endpoints was done. There was no statistically significant difference between the two approaches with regard to recurrence (odds ratio [OR], 1.22; 95% confidence interval [CI], 0.78-1.92), completeness of resection (OR, 1.17; 95% CI, 0.66-2.10), adjuvant therapy (OR, 0.71; 95% CI, 0.40-1.26), or thymoma-related deaths (OR, 0.76; 95% CI, 0.12-4.66). There was a statistically significant decrease in postoperative complications (OR, 0.61; 95% CI, 0.39-0.97), drainage (mean difference [MD], -0.99; 95% CI, -1.98 to -0.01), and length of hospital length (MD, -1.88; 95% CI, -3.39 to -0.36) with partial thymectomy. The evidence appeared to suggest that partial thymectomy is oncologically equivalent to complete thymectomy for non-myasthenic patients with early-stage thymoma. There is an additional advantage of reduced postoperative complications and decreased length of hospital stay with partial thymectomy.

Thymoma: Challenges and Pitfalls in Biopsy Interpretation

The interpretation of biopsy specimens in the diagnosis of thymoma is a subject that is generally not addressed in the literature. Even though the diagnosis of thymoma may seem to be an easy step in the assessment of these tumors, in reality, it is the biopsy specimen interpretation that will be use to determine course of action in any particular patient. It may determine whether a patient is a surgical candidate or on the contrary whether a patient may be benefited the most by medical therapy. In addition, there may be conditions in which all that is required is surgical resection without any further treatment, and that the evaluation of those conditions does not necessarily required the careful pathologic staging that thymomas need. In addition, it is important to highlight that in small biopsies, there are limitations not only in terms of the cellularity and other features that may not be present in such biopsy but also the limitation in term of immunohistochemical interpretation. Herein we have attempted to highlight numerous tumoral conditions that are frequently encountered in the daily practice of mediastinal pathology, some of them pose significant problems in separating them from thymomas. Needles to say, the entire spectrum of mediastinal pathology that may at any given time mimic thymoma is well beyond the scope of this review. Furthermore, we also herein emphasize the need for proper clinical and radiologic information and correlation in order to lead to a better interpretation of the biopsy specimen. The emphasis in this review is on thymoma and their possible pitfall and shortcomings while evaluating small biopsy specimens.

Thymoma Staging: An Analysis of the Different Schemas

Over the last years, a number of changes has taken place in the evaluation of thymomas. More recently, the introduction of a TNM staging system in the assessment of thymic epithelial tumors, in general, has been put forward. Important to highlight is that this TNM system is not based on tumor size, and because of that shortcoming, it was in need to borrow most if not all of the information from the experience derived from other schemas that over the years have been tested with larger series of cases. Also important to recognize is that this TNM system is nothing new as previous authors in the past had already attempted to provide a TNM system for thymomas without much success. Therefore, it becomes important that those involved with the staging of thymomas become familiar with previous schemas as the TNM system provides a slight different spin in the T component, while the M component truly represents advance stages of previous schemas. More importantly is to also highlight that despite the specific anatomic structures addressed in the T or M assessment, there is little information in the most important aspect of any staging system-clear definitions of invasion and metastasis and the gross assessment of these tumors to provide an accurate staging. Capsular integrity still remains paramount in such assessment. A critical assessment of TNM system compared with previously proposed staging systems and whether there is a real advancement in applying it is discussed as well as the gross assessment of these tumors to highlight the importance of the staging protocol.

EBV-Positive Primary Large B-Cell Lymphoma: The Role of Immunohistochemistry and XPO1 in the Diagnosis of Mediastinal Lymphomas

Primary mediastinal (thymic) large B-cell lymphoma (PMBL) is described as almost always negative for Epstein-Barr virus (EBV). In the context of a mediastinal lymphoma, the distinction between PMBL, classical Hodgkin lymphoma, diffuse large B-cell lymphoma, and mediastinal gray-zone lymphoma can be very difficult; hence, EBV positivity often argues against PMBL. We present a 19-year-old man with mediastinal mass morphologically consistent with PMBL. The tumor expressed classic immunophenotype, including positivity for CD20, CD19, MAL, OCT2, BOB1, BCL6, CD79a, and subset positivity for CD30. However, the tumor was EBV-positive by in situ hybridization. Next-generation sequencing detected somatic mutations in XPO1 (E571K), SMARCB1 (L356fs), and MYCC (T73A). Although the immunophenotype and XPO1 mutation are characteristic of PMBL, EBV expression is uncommon. Since EBV positivity can occur in rare PMBLs, it should not be the deciding factor in the diagnosis. This is the first EBV-positive PMBL in which mutational profiling has been reported. Aside from providing diagnostic support, the finding of the XPO1 E571K mutation may suggest a targeted therapeutic option.

Development of thymic tumor in [LSL:KrasG12D; Pdx1-CRE] mice, an adverse effect associated with accelerated pancreatic carcinogenesis

Pancreatic Ductal AdenoCarcinoma (PDAC) represents about 90% of pancreatic cancers. It is one of the most aggressive cancer, with a 5-year survival rate below 10% due to late diagnosis and poor therapeutic efficiency. This bad prognosis thus encourages intense research in order to better understand PDAC pathogenesis and molecular basis leading to the development of innovative therapeutic strategies. This research frequently involves the KC (LSL:KrasG12D;Pdx1-CRE) genetically engineered mouse model, which leads to pancreatic cancer predisposition. However, as frequently encountered in animal models, the KC mouse model also exhibits biases. Herein, we report a new adverse effect of KrasG12D mutation in KC mouse model. In our hands, 10% of KC mice developed clinical signs reaching pre-defined end-points between 100- and 150-days post-parturition, and associated with large thymic mass development. Histological and genetic analyses of this massive thymus enabled us (1) to characterize it as a highly proliferative thymic lymphoma and (2) to detect the unexpected recombination of the Lox-STOP-Lox cassette upstream KrasG12D allele and subsequent KRASG12D protein expression in all cells composing thymic masses. Finally, we highlighted that development of such thymic tumor was associated with accelerated pancreatic carcinogenesis, immune compartment disorganization, and in some cases, lung malignancies.