Primary mediastinal tumors. Part 1: tumors of the anterior mediastinum

Magnetic Resonance Elastography of Anterior Mediastinal Tumors

BACKGROUND

Preoperative differentiation of the types of mediastinal tumors is essential. Magnetic resonance (MR) elastography potentially provides a noninvasive method to assess the classification of mediastinal tumor subtypes.

PURPOSE

To evaluate the use of MR elastography in anterior mediastinal masses and to characterize the mechanical properties of tumors of different subtypes.

STUDY TYPE

Prospective.

SUBJECTS

189 patients with anterior mediastinal tumors (AMTs) confirmed by histopathology (62 thymomas, 53 thymic carcinomas, 57 lymphomas, and 17 germ cell tumors).

FIELD STRENGTH/SEQUENCE

A gradient echo-based 2D MR elastography sequence and a diffusion-weighted imaging (DWI) sequence at 3.0 T.

ASSESSMENT

Stiffness and apparent diffusion coefficients (ADC) were measured in AMTs using MR elastography-derived elastograms and DWI-derived ADC maps, respectively. The aim of this study is to identify whether MR elastography can differentiate between the histological subtypes of ATMs.

STATISTICAL TESTS

One-way analysis of variance (ANOVA), two-way ANOVA, Pearson's linear correlation coefficient (r), receiver operating characteristic (ROC) curve analysis; P < 0.05 was considered significant.

RESULTS

Lymphomas had significantly lower stiffness than other AMTs (4.0 ± 0.63 kPa vs. 4.8 ± 1.39 kPa). The mean stiffness of thymic carcinomas was significantly higher than that of other AMTs (5.6 ± 1.41 kPa vs. 4.2 ± 0.94 kPa). Using a cutoff value of 5.0 kPa, ROC analysis showed that lymphomas could be differentiated from other AMTs with an accuracy of 59%, sensitivity of 97%, and specificity of 38%. Using a cutoff value of 5.1 kPa, thymic carcinomas could be differentiated from other AMTs with an accuracy of 84%, sensitivity of 67%, and specificity of 90%. However, there was an overlap in the stiffness values of individual thymomas (4.2 ± 0.71; 3.9-4.5), thymic carcinomas (5.6 ± 1.41; 5.0-6.1), lymphomas (4.0 ± 0.63; 3.8-4.2), and germ cell tumors (4.5 ± 1.79; 3.3-5.6).

DATA CONCLUSION

MR elastography-derived stiffness may be used to evaluate AMTs of various histologies.

LEVEL OF EVIDENCE: 4

TECHNICAL EFFICACY

Stage 2.

The clinical significance of open vs. minimally invasive surgical approaches in the management of thymic epithelial tumors and myasthenia gravis

Though advancements have been made in the pharmacologic treatment of myasthenia gravis (MG), surgical resection is not only an option as a last line of defense for those patients who do not respond to medical therapy but also remains vital for those with thymic epithelial tumors (TET). While prior studies have shown the potential superiority of minimally invasive approaches via robotic- and video-assisted thoracoscopic surgery (RATS/VATS) for thymectomy compared to open surgery, in the setting of malignancies, this outcome delineation is controversial. As RATS/VATS may be associated with less post-operative complications in the treatment of TET, some surgeons argue that the open approach is necessary for complete resection (R0 resection) and to prevent potential seeding of the malignancy. In this review article, we will compare the efficacy and implications of the different surgical approaches and techniques themselves in performing a thymectomy for autoimmune and oncologic pathologies.

Privacy enhancing and generalizable deep learning with synthetic data for mediastinal neoplasm diagnosis

The success of deep learning (DL) relies heavily on training data from which DL models encapsulate information. Consequently, the development and deployment of DL models expose data to potential privacy breaches, which are particularly critical in data-sensitive contexts like medicine. We propose a new technique named DiffGuard that generates realistic and diverse synthetic medical images with annotations, even indistinguishable for experts, to replace real data for DL model training, which cuts off their direct connection and enhances privacy safety. We demonstrate that DiffGuard enhances privacy safety with much less data leakage and better resistance against privacy attacks on data and model. It also improves the accuracy and generalizability of DL models for segmentation and classification of mediastinal neoplasms in multi-center evaluation. We expect that our solution would enlighten the road to privacy-preserving DL for precision medicine, promote data and model sharing, and inspire more innovation on artificial-intelligence-generated-content technologies for medicine.

Upfront Thoracic Magnetic Resonance Imaging for the Evaluation of Thymic Lesions to Reduce Non-Therapeutic Diagnostic Thymectomy: A Narrative Review

Background: Thymic pathologies represent the most common lesions of the anterior mediastinum. They may be classified as malignant or benign. Current diagnostic pathways recommend an initial assessment with computed tomography (CT) imaging to delineate potentially malignant thymic lesions. Despite this, high rates of non-therapeutic thymectomy continue to be observed. This carries with it significant anaesthetic, operative, and post-operative risks, in addition to healthcare costs. Consequently, there is a growing interest in magnetic resonance imaging (MRI) as a primary diagnostic modality for lesions of the anterior mediastinum. This narrative review outlines the current approaches to the evaluation of thymic lesions, with a discussion of the strengths and limitations of CT and MRI imaging modalities. It also evaluates the current discourse on the use of upfront MRI for thymic and anterior mediastinal lesion assessment. Methods: A narrative review was performed following a search on the Medline database. Articles that were evaluated had explored the role of MRI on the evaluation of thymic and anterior mediastinal lesions. Results: Current work-up for thymic and anterior mediastinal lesions are highly variable and centre around the use of CT. Upfront MRI demonstrates a similar accuracy to CT for various thymic and anterior mediastinal pathologies; however, the efforts to integrate this approach into routine practice remain in their infancy, with no standardised guidelines that exist. Conclusions: This narrative review demonstrates that there is a paucity of evidence relating to the sensitivity and specificity of MRI compared to CT for thymic lesion analysis and their subsequent relationship with non-therapeutic thymectomy. Future prospective trials to assess the role of MRI in thymic lesion determination are required to understand whether MRI can more accurately characterise these lesions to reduce non-therapeutic thymectomy. Additionally, further research efforts are required to characterise best-practice methods for integrating MRI into diagnostic pathways for these lesions in a cost-effective and resource-conscious manner.

Distinguishing thymic cysts from low-risk thymomas via [18F]FDG PET/CT

BACKGROUND

Thymic cysts are a rare benign disease that needs to be distinguished from low-risk thymoma. [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is a non-invasive imaging technique used in the differential diagnosis of thymic epithelial tumours, but its usefulness for thymic cysts remains unclear. Our study evaluated the utility of visual findings and quantitative parameters of [18F]FDG PET/CT for differentiating between thymic cysts and low-risk thymomas.

METHODS

Patients who underwent preoperative [18F]FDG PET/CT followed by thymectomy for a thymic mass were retrospectively analyzed. The visual [18F]FDG PET/CT findings evaluated were PET visual grade, PET central metabolic defect, and CT shape. The quantitative [18F]FDG PET/CT parameters evaluated were PET maximum standardized uptake value (SUVmax), CT diameter (cm), and CT attenuation in Hounsfield units (HU). Findings and parameters for differentiating thymic cysts from low-risk thymomas were assessed using Pearson's chi-square test, the Mann-Whitney U-test, and receiver operating characteristics (ROC) curve analysis.

RESULTS

Seventy patients (18 thymic cysts and 52 low-risk thymomas) were finally included. Visual findings of PET visual grade (P < 0.001) and PET central metabolic defect (P < 0.001) showed significant differences between thymic cysts and low-risk thymomas, but CT shape did not. Among the quantitative parameters, PET SUVmax (P < 0.001), CT diameter (P < 0.001), and CT HU (P = 0.004) showed significant differences. In ROC analysis, PET SUVmax demonstrated the highest area under the curve (AUC) of 0.996 (P < 0.001), with a cut-off of equal to or less than 2.1 having a sensitivity of 100.0% and specificity of 94.2%. The AUC of PET SUVmax was significantly larger than that of CT diameter (P = 0.009) and CT HU (P = 0.004).

CONCLUSIONS

Among the [18F]FDG PET/CT parameters examined, low FDG uptake (SUVmax ≤ 2.1, equal to or less than the mediastinum) is a strong diagnostic marker for a thymic cyst. PET visual grade and central metabolic defect are easily accessible findings.

Spatiotemporal distribution of mediastinal neoplasms: A comprehensive multi-center study

OBJECTIVES

Mediastinal neoplasms are typical but uncommon thoracic diseases with increasing incidence and unfavorable prognoses. A comprehensive understanding of their spatiotemporal distribution is essential for accurate diagnosis and timely treatment. However, previous studies are limited in scale and data coverage. Therefore, this study aims to elucidate the distribution of mediastinal lesions, offering valuable insights into this disease.

MATERIALS AND METHODS

This multi-center, hospital-based observational study included 20 nationwide institutions. A retrospective search of electronic medical records from January 1st, 2009, to December 31st, 2020, was conducted, collecting sociodemographic data, computed tomography images, and pathologic diagnoses. Analysis focused on age, sex, time, location, and geographical region. Comparative assessments were made with global data from a multi-center database.

RESULTS

Among 7,765 cases, thymomas (30.7%), benign mediastinal cysts (23.4%), and neurogenic tumors (10.0%) were predominant. Distribution varied across mediastinal compartments, with thymomas (39.6%), benign cysts (28.1%), and neurogenic tumors (51.9%) most prevalent in the prevascular, visceral, and paravertebral mediastinum, respectively. Age-specific variations were notable, with germ cell tumors prominent in patients under 18 and aged 18-29, while thymomas were more common in patients over 30. The composition of mediastinal lesions across different regions of China remained relatively consistent, but it differs from that of the global population.

CONCLUSION

This study revealed significant heterogeneity in the spatiotemporal distribution of mediastinal neoplasms. These findings provide useful demographic data when considering the differential diagnosis of mediastinal lesions, and would be beneficial for tailoring disease prevention and control strategies.

Benign lesions of the mediastinum

Mediastinal tumours represent a heterogeneous group of entities derived from the manifold structures located in or adjacent to the mediastinum. Due to the occurrence of some of these tumours in characteristic mediastinal compartments, an anatomical subdivision of the mediastinum in the prevascular (anterior), visceral (middle), and paravertebral (posterior) is helpful for the differential diagnosis. Benign anterior mediastinal tumours linked to an enlargement of the thymic gland mainly consist of thymic cysts and several types of thymic hyperplasia: true thymic hyperplasia, rebound hyperplasia, lymphofollicular hyperplasia, and so-called thymic hyperplasia with lymphoepithelial sialadenitis (LESA)-like features. Mature teratomas, ectopic (para)thyroid tissue, and benign thymic tumours such as thymolipoma or thymofibrolipoma represent further typical tumours of the anterior mediastinum. Pericardial, bronchogenic, or oesophageal duplication cysts predominate in the middle mediastinum, whereas neurogenic tumours and myelolipomas are characteristic findings in the posterior compartment. Vascular tumours, lipomas, adenomatoid tumours, Castleman disease, or mediastinitis are further examples of less frequent tumours or tumorous lesions affecting the mediastinum. This review focuses on benign mediastinal lesions with an emphasis on benign tumours of the thymus. Besides histology, characteristic epidemiological and clinical aspects prerequisite for the correct diagnosis and patient management are discussed.

Thymoma in multiple endocrine neoplasia type 1: a case report and systematic review

BACKGROUND

Multiple endocrine neoplasia type 1 (MEN1) is a rare syndrome that combines endocrine and non-endocrine tumors. Thymic neuroendocrine tumors are uncommon components that predict poor prognosis in patients with MEN1. We aimed to summarize the clinical characteristics of thymoma in MEN1 by reviewing the current reports from the literature.

METHODS

A patient with multiple endocrine neoplasia type 1 (parathyroid hyperplasia, pituitary adenoma, and insulinoma) was found to have a 2 × 1.5 cm thymic mass during long-term follow-up. Thoracoscope surgery was performed, and a histopathology examination revealed WHO Type B3 thymoma. A pathogenic mutation of c.783 + 1G > A in the MEN1 gene was identified. We further searched PubMed and EMBASE for thymoma in association with MEN1.

RESULTS

A comprehensive overview of the literature concerning characteristics of MEN1-related thymoma was summarized. Clinical characteristics and differences between thymoma and thymic carcinoid are highlighted.

CONCLUSIONS

Besides carcinoid, other tumors, including thymoma, need to be identified for thymic space-occupying lesions in MEN1 patients. The impact of thymoma on the long-term prognosis of MEN1 patients needs further investigation.

MRI Findings and Differential Diagnosis of Anterior Mediastinal Solid Tumors

The anterior mediastinum is the most common location of mediastinal tumors, and thymic epithelial tumors are the most common mediastinal tumors. It is important to differentiate thymic epithelial tumors from malignant lymphomas and malignant germ cell tumors because of the different treatment strategies. Dynamic contrast-enhanced MRI and diffusion-weighted imaging can provide additional information on the differential diagnosis. Chemical shift imaging can detect tiny fat tissues in the lesion and is useful in differentiating thymic hyperplasia from other solid tumors such as thymomas. MRI findings reflect histopathological features of mediastinal tumors, and a comprehensive evaluation of MRI sequences is important for estimation of the histopathological features of the tumor. In this manuscript, we describe the MRI findings of anterior mediastinal solid tumors and the role of MRI in the differential diagnosis.

Pure mediastinal seminoma about a case report

Mediastinal Seminoma is one of the malignant germ cell tumors of the mediastinum. It is a rare tumor that represents only 1%-4% of mediastinal tumors. We report the case of a patient treated at the Oncology Center of Oujda for a pure primitive seminoma of the mediastinum, with a review of the literature to assess the epidemiological, clinical, therapeutic, and prognostic characteristics of this pathology. This is a 25-year-old man whose aunt is being treated for breast cancer and who complained of persistent dry cough with asthenia without any other associated signs. The initial imaging revealed a voluminous locally advanced tumor process in the anterior and middle mediastinum. Tumor markers Alpha-fetoprotein (AFP) and beta-subunit of chorionic gonadotrophic hormone (BHCG) were normal, as well as testicular ultrasound. The CT- guided transthoracic biopsy with anatomopathological study and immunohistochemistry was in favor of a pure seminoma. The treatment consisted of primary chemotherapy with BEP protocol. The response was favorable with a significant reduction in tumor size estimated at 90%. The residual tumor was inoperable due to its intimate contact with the vascular structures and was treated with external radiotherapy at a total dose of 36 Gy. The evolution at 20 months after treatment was in favor of a good clinical and radiological evolution.

Pan-mediastinal neoplasm diagnosis via nationwide federated learning: a multicentre cohort study

BACKGROUND

Mediastinal neoplasms are typical thoracic diseases with increasing incidence in the general global population and can lead to poor prognosis. In clinical practice, the mediastinum's complex anatomic structures and intertype confusion among different mediastinal neoplasm pathologies severely hinder accurate diagnosis. To solve these difficulties, we organised a multicentre national collaboration on the basis of privacy-secured federated learning and developed CAIMEN, an efficient chest CT-based artificial intelligence (AI) mediastinal neoplasm diagnosis system.

METHODS

In this multicentre cohort study, 7825 mediastinal neoplasm cases and 796 normal controls were collected from 24 centres in China to develop CAIMEN. We further enhanced CAIMEN with several novel algorithms in a multiview, knowledge-transferred, multilevel decision-making pattern. CAIMEN was tested by internal (929 cases at 15 centres), external (1216 cases at five centres and a real-world cohort of 11 162 cases), and human-AI (60 positive cases from four centres and radiologists from 15 institutions) test sets to evaluate its detection, segmentation, and classification performance.

FINDINGS

In the external test experiments, the area under the receiver operating characteristic curve for detecting mediastinal neoplasms of CAIMEN was 0·973 (95% CI 0·969-0·977). In the real-world cohort, CAIMEN detected 13 false-negative cases confirmed by radiologists. The dice score for segmenting mediastinal neoplasms of CAIMEN was 0·765 (0·738-0·792). The mediastinal neoplasm classification top-1 and top-3 accuracy of CAIMEN were 0·523 (0·497-0·554) and 0·799 (0·778-0·822), respectively. In the human-AI test experiments, CAIMEN outperformed clinicians with top-1 and top-3 accuracy of 0·500 (0·383-0·633) and 0·800 (0·700-0·900), respectively. Meanwhile, with assistance from the computer aided diagnosis software based on CAIMEN, the 46 clinicians improved their average top-1 accuracy by 19·1% (0·345-0·411) and top-3 accuracy by 13·0% (0·545-0·616).

INTERPRETATION

For mediastinal neoplasms, CAIMEN can produce high diagnostic accuracy and assist the diagnosis of human experts, showing its potential for clinical practice.

FUNDING

National Key R&D Program of China, National Natural Science Foundation of China, and Beijing Natural Science Foundation.

Diagnostic approach for mediastinal masses with radiopathological correlation

PURPOSE

Mediastinal masses have various histopathological and radiological findings. Although lymphoma is the most common type of tumor, thymic epithelial and neurogenic tumors are common in adults and children, respectively, but several other types are difficult to distinguish. No previous review has simply and clearly shown how to differentiate mediastinal masses.

METHOD

We conducted a review of the latest mediastinal classifications and mass differentiation methods, with a focus on neoplastic lesions. Both older and recent studies were searched, and imaging and histopathological findings of mediastinal masses were reviewed. Original simple-to-use differentiation flowcharts are presented.

RESULTS

Assessing localizations and internal characteristics is very important for mediastinal mass differentiation. The mass location and affected organ/tissue should be accurately assessed first, followed by more qualitative diagnosis, and optimization of the treatment strategy. In 2014, the International Thymic Malignancy Interest Group presented a new mediastinal clinical classification. In this classification, mediastinal masses are categorized into three groups according to location: prevascular (anterior)-, visceral (middle)-, and paravertebral (posterior)-compartment masses. Then, the internal characteristics and functional images are evaluated.

CONCLUSIONS

Differentiation of mediastinal masses is very difficult. However, if typical imaging findings and clinical characteristics are combined, reasonable differentiation is possible. In each patient, proper differential diagnosis may contribute to better treatment selection.

B3 thymoma mimicking poorly differentiated thyroid carcinoma: Diagnostic pitfalls of anterior mediastinal mass fine needle aspiration

B3 thymoma is a rare malignant type of thymic epithelial neoplasm found in the anterior mediastinum. Diagnosis of thymoma from fine needle aspiration (FNA) can be challenging due to the infrequency of sampling and its morphologic overlap with other entities such as squamous cell carcinoma, lymphoma or thyroid carcinoma. We report a case of B3 thymoma mimicking poorly differentiated thyroid carcinoma. We present its diagnostic pitfalls on cytology specimens, especially where it concerns identifying the correct location of the lesion, discuss the differential diagnosis, and correlation with the corresponding surgical resection specimen. A neck computed tomography angiogram (CTA) revealed a partially calcified 2.1 cm mass inferior to the left thyroid lobe in a 51 yr old woman being evaluated for stroke/TIA symptoms. She was referred for evaluation of the lesion. On the initial FNA and core needle biopsy, the lesion showed high-grade epithelioid cells with abundant lymphocytic infiltration and occasional necrosis, and was diagnosed as a high-grade carcinoma, favored to represent a poorly differentiated thyroid carcinoma considering the location on imaging. The patient subsequently underwent total thyroidectomy, central neck dissection, and thymectomy. Final surgical pathologic diagnosis indicated a type B3 thymoma. Due to the infrequency of sampling, thymoma poses a diagnostic challenge on preoperative FNA or core needle biopsy. Herein, we present a case of B3 thymoma with a preoperative cytologic specimen that consisted of hyperchromatic sheets of epithelioid tumor cells with a background of lymphocytes without definitive follicular cells or colloid. The core needle biopsy and cell block material showed abundant necrosis, intermixed lymphocytes and neoplastic epithelial cells with strong positive staining for pan-keratin and p40. The cytology and core needle biopsy material were interpreted as representing a probable thyroid neoplasm and raised a broad differential including anaplastic thyroid carcinoma, poorly differentiated thyroid carcinoma with squamous features, metastatic squamous carcinoma, and metastatic carcinoma to a lymph node. The final surgical resection specimen showed a B3 type-thymoma.

A neuroendocrine tumor within an anterior mediastinal mature teratoma: a case report

BACKGROUND

Mature teratomas are benign germ cell tumors. On rare occasions, they have been associated with somatic malignancies and are termed rare germ cell tumors with a somatic-type malignancy (GCTSM). Mature teratomas commonly comprise adenocarcinomas; only seven previous cases of mature teratomas with neuroendocrine tumors have been reported to date. Here, we report a patient with a neuroendocrine tumor whithin a mature teratoma.

CASE PRESENTATION

A 26-year-old man visited our department complaining of chest tightness. Contrast-enhanced computed tomography (CT) scans showed a strongly enhanced lesion within a 10-cm encapsulated cystic lesion in the anterior mediastinum. Positron emission tomography (PET) scans showed no areas of significant ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) accumulation. He underwent complete tumor resection via the transsternal approach. Histopathological examination of the specimen indicated a neuroendocrine tumor contained within a mature teratoma.

CONCLUSIONS

In this case, a neuroendocrine tumor was contained within a mature teratoma. Our patient had no specific symptoms and his serum markers were within the normal range. Although PET is beneficial for diagnosing other GCTSM, it is not useful in detecting a neuroendocrine tumor. Therefore, the preoperative diagnosis of neuroendocrine tumors contained within mature teratomas remains challenging. However, GCTSM should be suspected in patients exhibiting CT findings of a mediastinal tumor, measuring ≥ 6 cm, in addition to characteristic GCTSM findings. Moreover, surgery should be performed carefully in such cases.

Can MRI chemical shift imaging replace thymic biopsy in myasthenia gravis patients?

Background

Myasthenia gravis is a neuromuscular junction autoimmune condition characterized by muscle weakness. Many people with myasthenia gravis have thymic abnormalities, such as thymic lymphoid hyperplasia and thymic tumors, therefore, the thymus plays a significant role in the disease. The imaging properties of thymic hyperplasia and thymoma on CT and conventional MRI are very similar, yet, MRI has recently revealed promising capability by adding novel sequences. Chemical shift MRI was demonstrated to consistently distinguish thymic hyperplasia from thymus gland tumors. The aim of this study was to determine the value of chemical shift MRI imaging in characterizing thymic lesions in patients diagnosed with myasthenia gravis and its ability to differentiate thymic hyperplasia from thymoma.

Results

MRI showed that thymic lymphoid hyperplasia was more common to be convex in shape while thymoma was more likely to be round or irregular (P = 0.004). Paired comparison between histopathology and chemical shift MRI showed that MRI had 90% sensitivity and 100% specificity in detecting thymoma with overall diagnostic accuracy 93.3% (P = 0.5). MRI chemical shift ratio showed 100% sensitivity by using > 0.85 as a cut off value for diagnosis of thymoma, with specificity 83.3% (P = 0.0001). There was statistically significant difference in chemical shift ratio between thymic lymphoid hyperplasia and thymoma groups, as thymoma group had a higher chemical shift ratio of 1.06 ± 0.06 compared to 0.48 ± 0.13 in thymic hyperplasia group (P = 0.0001).

Conclusion

MRI chemical shift imaging with chemical shift ratio offers a highly sensitive and specific tool in assessment of thymus lesions in myasthenia gravis patients and it can differentiate between thymic hyperplasia and thymoma using cutoff value of > 0.85, hence, unwarranted invasive procedures as thymic biopsy or thymectomy can be avoided and proper management could be planned.

Carboplatin plus nanoparticle albumin‑bound paclitaxel for the treatment of thymic carcinoma

Thymic carcinoma is a relatively rare type of malignant tumor. The present retrospective study evaluated the efficacy and safety of carboplatin plus nanoparticle albumin-bound paclitaxel for the treatment of advanced thymic carcinoma. The study included data from 12 patients with advanced thymic carcinoma treated in the Nippon Medical School Hospital (Tokyo, Japan). Response to treatment, patient survival and treatment safety were assessed. The objective response rate was 66.7% (8/12 patients). Disease control was achieved in 11 patients (91.7%). At the median follow-up time of 27.6 months (range, 6.2-75.1 months), the median progression-free survival and median first-line overall survival times were 16.7 months [95% confidence interval (CI), 13.2-37.7] and 14.3 months (95% CI, 4.7-54.6), respectively. There was no occurrence of febrile neutropenia or treatment-related death. The results of the present study showed that carboplatin plus nanoparticle albumin-bound paclitaxel was effective and safe. Therefore, it is a promising chemotherapy regimen for the treatment of advanced thymic carcinoma.

Trends, Symptoms, and Outcomes of Resectable Giant Mediastinal Tumors

Describing the changes in surgical procedures and factors affecting the surgical outcome of patients who have undergone complete resection of giant mediastinal tumors (GMTs, diameter ≥ 10 centimeters) could improve preoperative decision-making and prognostic evaluations. We accessed data from three sources, which are case reports on surgical treatment of GMTs from PubMed, Web of Science, and EMBASE until June 1, 2019; patients with resected GMT from the Surveillance, Epidemiology, and End Results (SEER) database; and retrospective review of medical records in our institution from 2000 to 2019. The worldwide distribution, clinicopathological characteristics, symptom profile, prognosis of patients with GMT resection, and nomogram for surgical outcome prediction are reported. A total of 242 rare GMT cases from four continents (Asia, North America, South America, and Europe) were included. The median age of the patients was 40 (IQR: 27, range: 13–83) years, and the male-to-female ratio was 1.57:1. Dyspnea, shortness of breath, cough, and chest pain or discomfort were the major symptoms at presentation. The prognosis of benign and low-grade malignant GMTs was superior to that of high-grade malignant GMTs. Tumor malignancy played the most critical role in predicting postoperative survival, followed by longest tumor diameter and a posterior mediastinum location. The findings of this study suggest that the number of successful GMT surgeries has increased over the last decade and describe clinical features of GMTs. Physicians should prioritize tumor malignancy as a leading factor in predicting outcome rather than tumor size.

[Mediastinal lesions : The most common pathologies in chest X-rays and their correlations in computed tomography]

BACKGROUND

Many pathologies of the mediastinum can be diagnosed using standard radiographs. Correlation of radiographic findings with computed tomography (CT) is instructive for a better understanding and can help improve detection rates of mediastinal lesions.

OBJECTIVES

To identify the most common mediastinal lesions and to correlate their features in chest radiographs and CT.

METHODS

The International Thymic Malignancy Interest Group (ITMIG) classification in the anterior, middle, and posterior mediastinum is based on anatomic landmarks. Used as a tool to characterize mediastinal lesions this classification is applied in this article.

RESULTS

The most common lesions include mediastinal goiter, germ cell and thymic neoplasms in the anterior mediastinum, lymphadenopathy in the middle mediastinum, and neurogenic neoplasms in the posterior mediastinum. Other lesions of neoplastic or non-neoplastic origin can be distinguished in the three compartments and should be considered in the differential diagnosis.

CONCLUSIONS

Knowledge of the most common pathologies in the three mediastinal compartments can accelerate differential diagnosis. Understanding the normal mediastinal lines is key in anatomic localization and detection of many lesions in chest radiographs.

Clinical usefulness of PET/MRI in differentiating anterior mediastinal masses

OBJECTIVES

To investigate the clinical usefulness of 18F-fluorodeoxyglucose (FDG) PET/MRI in differentiating anterior mediastinal lesions, including small ones.

MATERIAL AND METHODS

Among 96 patients who underwent 18F-FDG PET/MRI screening for anterior mediastinal lesions, we retrospectively reviewed images of 42 patients with histologically or clinically diagnosed thymic carcinomas, thymomas or anterior mediastinal cysts. MRI findings and maximum standardized uptake value (SUVmax) were compared among the three categories. In addition, small lesions measuring <3.0 cm which did not show very high signal intensity (isointense to water) on T2 weighted images (T2WI) were sub-analyzed.

RESULTS

Significant differences in SUVmax were observed among anterior mediastinal cysts (P < 0.001, vs. thymomas and thymic carcinomas), thymomas (P = 0.032, vs. thymic carcinomas) and thymic carcinomas. Regarding the MRI findings, anterior mediastinal cysts showed higher T2WI signal intensity (P = 0.004 vs. thymomas and P = 0.042 vs. thymic carcinomas) and thymic carcinomas tended to show ill-defined contours (P = 0.024 vs. anterior mediastinal cysts and P = 0.036 vs. thymomas). SUVmax was also significantly higher in small thymic tumors than small anterior mediastinal cysts without very high T2WI signal intensity (P = 0.003).

CONCLUSION

18F-FDG PET/MRI is clinically useful in differentiating anterior mediastinal lesions, including those smaller than 3 cm.

Short-term analysis of uniport video-assisted thoracoscopic surgery via the subxiphoid approach without chest tube drainage for anterior mediastinal tumors: a comparative retrospective study

Background

Uniport video-assisted thoracoscopic surgery (VATS) via the subxiphoid approach has emerged as a safe and effective treatment for anterior mediastinal tumors. However, there is limited evidence of the necessity of chest tubes and the comparative efficacy with other approaches.

Methods

A total of 141 patients with anterior mediastinal tumors receiving VATS were enrolled in this retrospective study. The patients were divided into the lateral approach (LA) group, the uniport subxiphoid approach (USA) group, and the three-port subxiphoid approach (TSA) group. Short-term analysis including operation time, chest tube rates, drainage duration, visual analogue scale (VAS) score, and hospital stay were compared. Postoperative CT scans were analyzed to evaluate the amount of pleural effusion.

Results

There was no significant difference in demographic and baseline characteristics among the three groups (all P>0.05). The operation time, blood loss, and hospital stay of the subxiphoid approach group were significantly lower than the LA group (P<0.001). The postoperative CT scans demonstrated that the USA group had a similar amount of pleural effusion as the other groups (P=0.1605). The postoperative VAS score of the USA group was significantly lower than the other groups (P<0.001). There was no significant difference in complications, in-hospital death, and conversion to thoracotomy among the three groups (all P>0.05).

Conclusions

VATS via the subxiphoid approach is less invasive, equally safe, and same effective for anterior mediastinal tumors than the LA. The chest tube could be omitted for the USA.

Not Your Average Mediastinal Mass: A Case of a Large Mediastinal Teratoma in a Patient With a History of Polio Disease

Mediastinal masses can be challenging to the surgical team and anesthetic considerations vary according to the location, pathology, surgical approach, and patient comorbidities. We report the case of a 21 cm symptomatic intrathoracic teratoma in a postpartum patient with a history of poliomyelitis. Significant challenges were presented for anesthetic induction, potential extracorporeal membrane oxygenation, and the use of neuraxial pain techniques and neuromuscular blockade. This case report demonstrates techniques to safely manage a patient with a large symptomatic mediastinal mass and potential neuromuscular disease.

Epicardial carvernous hemangioma: The diagnostic challenge of a middle mediastinal mass

Primary tumors in the middle mediastinum are rare and pose diagnostic challenges. Lymphomas, mediastinal cysts and thymomas most frequently affect this anatomic area. Primary cardiac tumors are rare and constitute a differential diagnosis for the inferior middle mediastinum. Surgical exploration and resection is often mandatory in order to make a definitive diagnosis. Here, we report the case of a 69 year-old women who presented with persistent dyspnea. A complete preoperative workup revealed a large tissular mass adjacent to the right atrium. A diagnosis of a typical epicardial cavernous hemangioma was made following surgical resection.

Mucoepidermoid carcinoma of the thymus incidentally diagnosed following two-years of non-productive cough

Mucoepidermoid carcinoma of the thymus is a rare primary thymic carcinoma. Radiologic imaging of this malignancy is rarely reported in literature. We present a patient who complained of a chronic cough for two years who was later found to have mucoepidermoid carcinoma of the thymus. Chest radiograph revealed a large anterior mediastinal mass. Follow-up computed tomography of the thorax demonstrated a large, heterogeneous anterior mediastinal mass with traversing vessels. F-18 fluorodeoxyglucose positron emission tomography-computed tomography demonstrated high avidity in the lesion with areas of diminished activity thought to represent necrosis. Following surgical resection, pathology revealed high-grade mucoepidermoid carcinoma of the thymus extending into the skeletal muscle and pericardium with evidence of lymphovascular invasion. The patient received external beam radiation therapy and has remained disease-free for three years.

Calcification in thymomas can predict invasiveness to surrounding organs

BACKGROUND

Thymomas are the most common type of anterior mediastinal tumors. Calcification is sometimes observed in thymomas using computed tomography (CT), and it is more frequent in invasive thymomas than in noninvasive thymomas. However, the significance of calcification in thymomas remains unknown. This study aimed to evaluate the significance of calcification in thymomas on invasiveness to surrounding organs and investigate the characteristics of thymoma cases with calcification at our institution.

METHODS

We included thymoma patients treated at our institution between 2000 and 2016, and evaluated their characteristics, including demographics, calcification on CT, histology, Masaoka stage, and myasthenia gravis status. The patients were categorized into calcification (C) and noncalcification (NC) groups.

RESULTS

Among 51 included patients, 11 (21.6%) had calcification. A higher proportion of group C patients had World Health Organization histological type B2 and B3 tumors (high-risk) than type A, AB, and B1 tumors (low-risk; p = 0.0477). The number of patients with Masaoka stages III and IV were significantly higher in the C group than in the NC group (p < 0.0001). The C group patients had significantly higher rates of invasion to the mediastinal pleura, pericardium, lung, phrenic nerve, and chest wall and pleural dissemination than the NC group patients.

CONCLUSIONS

Calcification reflects invasiveness of tumors to surrounding organs and tissues, and may thus predict thymoma stage and histologically high-risk thymomas. Calcification in thymomas may also predict the pathological stage and help decide therapeutic methods and surgical approaches to treat thymomas based on the calcification status according to CT findings.

A Rare Case of Primary Pericardial Schwannoma

Schwannomas are typically benign, indolent neoplasms. Primary pericardial schwannomas are extremely rare and arise from the cardiac plexus and vagus nerve innervating the heart. Few case reports have been documented to date. Pericardial schwannomas are difficult to diagnose at plain radiography or transthoracic echocardiography, often leading to further characterization with either CT or MRI. Biopsy is required for definitive diagnosis. A case of primary pericardial schwannoma of the posterior pericardium with concerns for compression of the left atrium and left ventricle is presented. © RSNA, 2021.

Imaging of the Anterior/Prevascular Mediastinum

Prevascular mediastinal masses include a wide range of benign and malignant entities. Localization of mediastinal masses to specific compartments together with characteristic imaging findings and demographic and clinical information allows formulation of a focused differential diagnosis. Radiologists may use these methods to distinguish between surgical and nonsurgical cases and thus inform patient management and have an impact on outcomes. Treatment of choice varies based on the pathology, ranging from no intervention or serial imaging follow-up to surgical excision, chemotherapy, and/or radiation.

Thymic Epithelial Neoplasms: Radiologic-Pathologic Correlation

Thymic epithelial neoplasms, as classified by the World Health Organization, include thymoma, thymic carcinoma, and thymic carcinoid. They are a rare group of tumors and are often diagnosed incidentally in the work-up of parathymic syndrome, such as myasthenia gravis, or when mass effect or local invasion causes other symptoms. In each of these scenarios, understanding the radiologic-pathologic relationship of these tumors allows clinical imagers to contribute meaningfully to management decisions and overall patient care. Integrating important imaging features, such as local invasion, and pathologic features, such as necrosis and immunohistochemistry, ensures a meaningful contribution by clinical imagers to the care team.

Role of Endobronchial Ultrasound-guided Transbronchial Needle Aspiration in the Diagnosis and Management of Mediastinal Cyst

BACKGROUND

Foregut cysts account for >50% of cystic lesions in the mediastinum, of which bronchogenic cysts are most common. Surgical resection is the most definitive approach for its diagnosis and treatment. A recent systematic review, however, suggests that endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has a role in the management of bronchogenic cyst. We report our experience with EBUS-TBNA in the diagnosis and management of bronchogenic cysts.

METHODS

Medical records of patients with evidence of mediastinal cysts who underwent EBUS-TBNA between 2008 and 2016 were reviewed.The primary aims of this study were to assess EBUS-TBNA diagnostic yield of peri-bronchial cysts and their specific type/origin and to determine its short-term and long-term drainage efficacy.

RESULTS

A total of 26 patients met the inclusion criteria. The cytopathology diagnosis was compatible with bronchogenic cyst in 4 cases, pleural-pericardial cyst in 3 cases, and 19 were indeterminate cysts. Successful long-term treatment occurred in 5.5% of the subjects. One patient developed inflammatory pericarditis after EBUS-TBNA.

CONCLUSION

Diagnostic and therapeutic yield of EBUS-TBNA for mediastinal cysts is limited and surgical resection remains the treatment of choice.

Mediastinal teratoma presenting as a cervical tumor: images

Benign extra-gonadal germ cell tumors, known as teratoma or dermoid cysts, are commonly found in the anterior mediastinum in association with the thymic gland. This association is due to their common site of embryological origins, from the third and the fourth pharyngeal pouches. Since it is not unusual to find normal thymic tissue in the neck, germ cell tumors arising from here will present as a cervical tumor. We submit the typical images of one such tumor in a young adult. Intraoperatively, the tumor was well encapsulated and was connected to the mediastinal thymus by a long pedicle of thymic tissue. It was not related to the thyroid gland unlike a primary cervical teratoma. We present these typical images of a mediastinal dermoid in this unusual cervical location. The differential diagnoses to be considered clinically are primary cervical teratomas, thyroid tumors, lymph nodal pathologies, and branchial cyst.

Anterior mediastinal lesions: CT and MRI features and differential diagnosis

Anterior mediastinum is the most common location of mediastinal tumors, which include various solid and cystic lesions. The lesion location and CT and MRI features are important in the differential diagnosis. Recently, CT-based mediastinal compartment classification systems were proposed and suggested to be useful for accurate evaluation of mediastinal lesions. CT and MRI reflect the pathological findings of mediastinal lesions, and knowledge of the pathological features is important for the differential diagnosis. In this article, we review the CT and MRI features of anterior mediastinal lesions and describe important points in the differential diagnosis.

Long-term outcome in mediastinal malignancies: video-assisted thoracoscopic versus open surgery

Purpose

There are not many studies comparing long-term oncological outcomes between video-assisted thoracoscopic surgery (VATS) and open surgery for mediastinal malignancies. This study aimed to compare perioperative and long-term outcomes of these two techniques in the treatment of mediastinal malignancies.

Methods

This is a retrospective study: patients with mediastinal malignancies underwent VATS or open surgery from 2010 to 2013 and were followed until 2019. The primary endpoints were long-term oncological outcomes, including tumor recurrence and mortality. Secondary endpoints were perioperative outcomes (operative duration, blood loss, pain, chest drainage duration, hospital length of stay, and complications).

Results

There were 36 patients in the VATS group and 49 patients in the open group. The median follow-up duration was 90 months. VATS significantly reduced operation time (84.6 versus 124.8 min), blood loss (59.8 versus 235.2 ml), postoperative pain score (4.9 versus 6.7), the duration of chest tube drainage (2.1 versus 3.1 days), and postoperative hospital stay (5.2 versus 8.0 days). The two groups were comparable regarding the recurrence rate (2.4 versus 2.1/100 person-years) and mortality rate (0.8 versus 0.9/100 person-years).

Conclusion

Compared with open surgery, VATS is less traumatic, reduces postoperative chest drainage, and shortens hospital stay with comparable long-term oncological outcomes. We advocate the VATS approach as a favored option for the resection of mediastinal malignancies.

Pictorial Review of Mediastinal Masses with an Emphasis on Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) has become a crucial tool for evaluating mediastinal masses considering that several lesions that appear indeterminate on computed tomography and radiography can be differentiated on MRI. Using a three-compartment model to localize the mass and employing a basic knowledge of MRI, radiologists can easily diagnose mediastinal masses. Here, we review the use of MRI in evaluating mediastinal masses and present the images of various mediastinal masses categorized using the International Thymic Malignancy Interest Group's three-compartment classification system. These masses include thymic hyperplasia, thymic cyst, pericardial cyst, thymoma, mediastinal hemangioma, lymphoma, mature teratoma, bronchogenic cyst, esophageal duplication cyst, mediastinal thyroid carcinoma originating from ectopic thyroid tissue, mediastinal liposarcoma, mediastinal pancreatic pseudocyst, neurogenic tumor, meningocele, and plasmacytoma.

Heart rupture repair during huge mediastinal mass resection - case report

BACKGROUND

Ventricular rupture is rarely described in the literature outside the context of myocardial infarction, infection or neoplasm. It is associated with a high mortality rate due to late presentation and delayed surgical intervention, which involves sutureless or sutured techniques. Comprehensive literature review failed to identify any case of intra-operative right ventricular heart rupture followed by myocardial repair and a complete recovery after a prolonged intensive care unit (ICU) stay.

CASE PRESENTATION

A 57-year-old previously healthy gentleman presented complaining of a new onset shortness of breath for 2 months. A large mediastinal mass was found on chest imaging and biopsy revealed a thymoma. Patient received a neoadjuvant Cisplatin/Doxorubicin/Cyclophosphamide (CAP) regimen chemotherapy then sternotomy and thymectomy en bloc with anterior pericardium. Post-thymectomy, the patient continued to be hypotensive in recovery despite aggressive fluid resuscitation. He was sent back to theatre, aggressive fluid resuscitation continued, surgical site exploration was done by reopening the sternum, and the bleeding source was identified and controlled, but intraoperative asystole developed. During internal cardiac massage, the right ventricle ruptured with a 3 cm defect which was successfully repaired using a pericardial patch without a bypass machine due to unavailability at our cancer center. The patient remained dependent on mechanical ventilation through tracheostomy for a total of 2 months due to bilateral phrenic nerve paralysis, was discharged from ICU to the surgical floor 66 days after the operation and weaned off ventilator support after 85 days, adequate respiratory and physical rehabilitation followed. Patient is doing very well now with excellent performance, and free of tumor recurrence 30 months after surgery.

CONCLUSION

Right ventricular rupture is rarely described outside the context of myocardial infarction and valvular heart disease. Tumor proximity to the heart and neoadjuvant cardiotoxic chemotherapy are the proposed causes for precipitating the cardiac rupture in our case. Post-surgical patients who receive early physical rehabilitation and respiratory physiotherapy have improved survival and outcome.

The role of positron emission tomography/computed tomography in the evaluation of anterior mediastinal masses and differentiating between the histological subtypes of thymic epithelial neoplasms

Background

This study aims to investigate the role of positron emission tomography/computed tomography in differentiating between benign and malignant anterior mediastinal masses and between the histological subtypes of thymic epithelial neoplasms.

Methods

This retrospective study included a total of 57 patients (30 males, 27 females; mean age 48.9 years; range, 14 to 78 years) who underwent an fluorodeoxyglucose positron emission tomography/ computed tomography with an indication of an anterior mediastinal mass between May 2010 and November 2018. The maximum and mean standardized uptake values, metabolic tumor volume, total lesion glycolysis, and mean Hounsfield units of the lesions were determined. Thymic epithelial neoplasms were classified as low-risk thymomas (A, AB, B1), high-risk thymomas (B2, B3), and thymic carcinomas. All lesions were evaluated together and divided into two groups as benign and malignant, and positron emission tomography/computed tomography parameters of the two groups were compared.

Results

Histopathological examination identified 29 thymic epithelial neoplasms (13 low-risk, 14 high-risk, two thymic carcinomas), 13 benign lesions, and 15 malignant lesions. No significant correlation was identified between the positron emission tomography/computed tomography parameters and histological subtype of thymic epithelial neoplasms. There was no significant difference in the maximum and mean standardized uptake values, metabolic tumor volume, total lesion glycolysis, and mean Hounsfield units of the lesions between low-risk and high-risk thymic carcinomas. The maximum and mean standardized uptake values, metabolic tumor volume, and mean Hounsfield units of the lesions were significantly higher in the malignant group than in the benign group.

Conclusion

Our study results show that positron emission tomography/ computed tomography is useful in the differentiation of benign and malignant anterior mediastinal masses, although it fails to differentiate between the histological subtypes of thymic epithelial neoplasms.

Role of different imaging modalities in the evaluation of normal and diseased thymus

Background

The appearance of the thymus on imaging studies showed great variability. Thymus imaging is a great challenge. This cross-sectional prospective study investigated the diagnostic value of different imaging modalities in the evaluation of normal and diseased thymus. Chest X-ray was done as a primary survey. Chest computed tomography (CT) was done for 82 patients, chest magnetic resonant imaging (MRI) was done for 40 patients, and 18 flurodeoxy glucose positron emission tomography (18 FDG-PET) was done for 2 patients. Ultrasonography (US) of the anterior mediastinum was done for 2 pediatric patients. Histopathological assessment was done for all cases with diseased thymus.

Results

The study included 158 patients divided into 2 groups: group A, 79 patients with normal thymus for age and group B, 79 patients with thymic lesions detected by one or more of the used modalities. The large-sized thymus was in 79 patients, who were subcategorized to patients with myasthenia gravis (12 patients) and patients with mediastinal masses (67 patients). Imaging findings in normal and diseased thymus gland were compared and lesion analysis by various modalities displayed with histopathological correlation.

Conclusion

There are different imaging modalities for thymus gland evaluation. CT is beneficial for primary assessment giving the morphology and density, and MRI is the imaging modality of choice in diseased thymus owing to functional assessment of the gland; however, X-ray may be helpful as a primary survey tool before CT and MRI. Chest ultrasound could be a suitable primary assessment tool in pediatrics before MRI because it is an easy bedside test.

Differentiating thymoma from thymic cyst in anterior mediastinal abnormalities smaller than 3 cm

Background

Computed tomography (CT) screening for lung cancer has led to frequent findings of small anterior mediastinal masses. It is very hard to distinguish small thymomas from thymic cysts. The objective of this study was to develop a clinical model for predicting small thymomas (<3 cm) in asymptomatic patients.

Methods

Patients who underwent thymectomy for anterior mediastinal masses between 2004 and 2016 were included. All preoperative CT scans (pre- and post-enhanced) were retrospectively reviewed. Size, location, contour, shape, presence of calcification, and enhancement [Hounsfield units (HU)] were evaluated. A nomogram was built based on the predictive factors. For external validation, patients undergoing thymectomy in 2017 were enrolled and thymoma prediction was computed using the proposed nomogram.

Results

The study population consisted of 43 patients with thymoma and 57 with thymic cyst. The multivariable analysis identified a lobulated contour and a large difference in HU between post- and pre-enhancement as predictive factors of thymoma. These factors were included in the nomogram, which showed 95% (19/20) power for predicting thymoma after external validation.

Conclusions

This clinical model can be used to predict thymoma in patients with small, asymptomatic thymic abnormalities on CT screening.

Contrast-enhanced ultrasound features of mediastinal lymphomas and thymic epithelial tumors

OBJECTIVES

To summarize the contrast-enhanced ultrasound (CEUS) features of mediastinal lymphomas and thymic epithelial tumors (including thymomas and thymic carcinomas) and to explore the value of CEUS in the differential diagnosis of lymphomas and thymic epithelial tumors.

METHODS

Sixty-nine patients with 69 mediastinal lesions who underwent CEUS and had disease confirmed by histopathology were enrolled in the study. There were 33 cases of lymphoma, 19 cases of thymic carcinoma, and 17 cases of thymoma. CEUS features, including the enhancement pattern, enhancement distribution, enhancement time, inner necrosis status, wash out pattern, and vascular morphology, were evaluated in each group.

RESULTS

Thymomas often presented with homogeneous (88.2%, 15/17) and late (88.2%, 15/17) enhancement and a low rate of inner necrosis (17.6%, 3/17). Late (73.7%, 14/19), heterogeneous (68.4%, 13/19), and centripetal (63.2%, 12/19) enhancement were more often observed in thymic carcinoma, as was a high rate of inner necrosis (78.9%, 15/19). Lymphomas showed a homogeneous enhancement rate of 57.6% (19/33) and a late enhancement rate of 54.5% (18/33). The rate of inner necrosis for lymphomas was 45.5% (15/33). The diagnostic accuracy of this finding for distinguishing thymic epithelial tumors from lymphomas was 63.8%, the sensitivity was 80.6%, and the specificity was 45.5%. Enlarged blood vessels were a feature specific to lymphomas, while small vessels arranged in a comb shape was a feature specific to thymic epithelial tumors.

CONCLUSION

This study describes the CEUS features of common mediastinal tumors and may stimulate further studies in this field.

A case of mediastinal teratoma with pancreatic islets accompanied by discontinuation of insulin treatment in insulin-dependent diabetes mellitus

A 74-year-old woman of insulin-dependent diabetes mellitus presented with gradually improvement of blood glucose control and finally discontinuation of insulin therapy, for some unknown reason. During follow-up period, she was admitted with hemoptysis. CT imaging showed a heterogeneous enhancement mass in the middle mediastinum with cyst and calcification, suggesting the diagnosis of mediastinal teratoma. Immediately after excision of the tumor, her plasma glucose levels again increased, and she required insulin therapy for glycemic control. Immunohistochemical examination showed that the tumor contained pancreatic tissue with both exocrine and endocrine components consisted with the islet cells of Langerhans with insulin-positive cells. Accordingly, we diagnosed insulin-producing mediastinal teratoma. Although hypoglycemic agents are the commonest cause of hypoglycemia in diabetic patients, an insulin-producing tumor should be considered in the patients who have dramatic improvement of diabetes mellitus, particularly after withdrawal of all hypoglycemic treatment. Mediastinal teratomas should be considered in differential diagnosis as etiology in undiagnosed case of hypoglycemia or blood glucose fluctuations.

A Population-Based Study of Incidence and Survival of 1588 Thymic Malignancies: Results From the California Cancer Registry

BACKGROUND

Thymic malignancies are rare and there are limited contemporary population-based epidemiological studies for this uncommon cancer.

PATIENTS AND METHODS

Adults aged 20 years and older diagnosed with thymic malignancies between 1988 and 2015 were identified from the California Cancer Registry (n = 1588). Trends in age-adjusted incidence rates were examined overall and according to race/ethnicity, and the proportion diagnosed according to stage was evaluated over time. Cox proportional hazards regression was used to estimate hazard ratios (HRs) for overall survival (OS), and Fine and Gray competing risks regression for cause-specific survival (CSS).

RESULTS

Age-adjusted incidence increased on average 2.08% per year over the study period (95% confidence interval [CI], 1.30%-2.86%; P < .0001), with an incidence of 0.277 cases per 100,000 in 2015. Incidence was highest among Asian/Pacific Islander and non-Hispanic black individuals. The proportion of unknown stage at diagnosis declined as localized diagnoses increased over time. Compared with patients with thymoma, those with thymic carcinoma had significantly worse OS (HR, 1.63; 95% CI, 1.33-2.01; P < .0001) and CSS (subdistribution HR, 2.99; 95% CI, 2.29-3.91; P < .0001). Advanced stage at diagnosis was also associated with worse survival. Surgical intervention was associated with better prognosis for patients with localized (HR, 0.08; 95% CI, 0.02-0.30; P = .0002) or regional disease (HR, 0.14; 95% CI, 0.06-0.34; P < .0001).

CONCLUSION

Thymic malignancy incidence is increasing in California. There was incidence variation across race/ethnicity, which warrants future study. These findings provide contemporary insight into the incidence and prognostic factors of thymic malignancies.

Comparison between CT and MRI in the Diagnostic Accuracy of Thymic Masses

Purpose: The aim of this study was to compare diagnostic accuracy between CT and MRI for thymic masses.

Methods: We searched literature and collected information on first author, publication year, cases of different types of thymic lesions, correct diagnostic cases of CT and MRI and results of quantitative analysis of CT and MRI. The ROC curve was applied to compare the diagnostic performance of different imaging modalities.

Results: Eight literatures were finally included and analyzed in this study. There were 253 cases examined by CT and 340 cases by MRI in total. We showed outcomes of quantitative analysis of each study in this article. The sensitivity of CT and MRI was both 100%, while the specificity was 75% and 80%, respectively. AUC of CT was 0.875 [95%CI: 0.473, 0.997] and that of MRI was 0.880 [95%CI: 0.531, 0.995].

Conclusion: The diagnostic accuracy of MRI is superior to CT in detecting thymomas, thymic cysts or thymic hyperplasia but that of CT and MRI is still unclear in differentiating thymic carcinomas and lymphomas/germ cell tumors.

Giant intrathoracic teratoma presenting with cachexia and severe dyspnea

Background

This case highlights the challenges of preoperative differential diagnosis and management in a patient with an uncommon clinical presentation of giant intrathoracic teratoma. The age of the patient, location and size of the tumor, and clinical presentation makes this case unique. Typically, intrathoracic teratomas are found between the ages of 20–30, they are located in the anterior mediastinum, and tumors larger than 25 cm clinically present with cough or dysphagia.

Case presentation

A giant intrathoracic teratoma presents in a 51-year-old female as a mid to posterior mediastinal mass compressing the whole left lung with symptoms of depression, anorexia, unintentional weight loss, and cachexia. Due to her severe deconditioning she was optimized for 1 month in a skilled nursing facility with aggressive physical therapy and enteral nutrition. She underwent left thoracotomy with complete resection of the tumor. In follow up her BMI had improved, and she was regaining strength.

Conclusions

Complete resection was achieved via left thoracotomy after aggressive rehabilitation.

CT-based radiomics features analysis for predicting the risk of anterior mediastinal lesions

Background

To retrospectively validate CT-based radiomics features for predicting the risk of anterior mediastinal lesions.

Methods

A retrospective study was performed through February 2013 to March 2018 on 298 patients who had pathologically confirmed anterior mediastinal lesions. The patients all underwent CT scans before their treatment, including 130 unenhanced computed tomography (UECT) and 168 contrast-enhanced CT (CECT) scans. The lesion areas were delineated, and a total of 1,029 radiomics features were extracted. The least absolute shrinkage and selection operator (Lasso) algorithm method was used to select the radiomics features significantly associated with discrimination of high-risk from low-risk lesions in the anterior mediastinum. Then, 8-fold and 3-fold cross-validation logistic regression (LR) models were taken as the feature selection classifiers to build the radiomics models for UECT and CECT scan respectively. The predictive performance of the radiomics features was evaluated based on the receiver operating characteristics (ROC) curve.

Results

Each of the two radiomics classifiers included the optimal 12 radiomic features. In terms of the area under ROC curve, using the radiomics model in discriminating high-risk lesions from the low-risks, CECT images accounted for 74.1% with a sensitivity of 66.67% and specificity of 64.81%. Meanwhile, UECT images were 84.2% with a sensitivity of 71.43% and specificity of 74.07%.

Conclusions

The association of the two proposed CT-based radiomics features with the discrimination of high and low-risk lesions in anterior mediastinum was confirmed, and the radiomics features of the UECT scan were proven to have better prediction performance than the CECT's in risk grading.

Age- and gender-specific disease distribution and the diagnostic accuracy of CT for resected anterior mediastinal lesions

Background

Anterior mediastinal lesions account for approximately half of all mediastinal masses and computed tomography (CT) is known to exhibit limited differentiating performance. Our aim was to evaluate the age‐ and gender‐specific distribution of anterior mediastinal lesions and the diagnostic accuracy of multi‐detector CT (MDCT).

Methods

This retrospective study included 549 consecutive patients with proven anterior mediastinal lesions and diagnostic MDCT scans. The age‐ and gender‐specific distribution of proven diagnoses and diagnostic accuracy were reviewed. The CT features of malignant and benign diseases having the lowest accuracy were compared with those of the most commonly misdiagnosed diseases.

Results

The proportion of malignancy showed a V‐shape relationship with age (lowest, 52.7% [50s]). The most prevalent malignancies were lymphoma (20s), lymphoma/thymoma (30s), thymoma (40s–50s), and thymoma/thymic carcinoma (≥60s). The most prevalent benign diseases were thymic remnant/hyperplasia (20s–30s), and thymic bed cyst (≥40s). The first‐choice diagnostic accuracy of MDCT decreased with age regardless of gender: 75.4% (20s), 75.0% (30s), 67.8% (40s), 58.5% (50s), and 53.4% (≥60s), primarily due to incorrect diagnoses of thymic bed cyst and thymic carcinoma (accuracy, 42.3% and 30.5%), which were prevalent in older patients and mostly misdiagnosed as thymoma. The most powerful differentiating MDCT features were water attenuation (≤20 HU) (OR, 42.7 [95%CI, 8.8–‐208.3], P < 0.001) for thymic bed cyst and mediastinal lymphadenopathy (6.8 [1.7–27.2], P = 0.006) for thymic carcinoma, but both showed low sensitivity (34.5% and 18.6%, respectively).

Conclusions

MDCT accuracy depended on age, owing to the age‐specific distribution of thymic carcinoma and thymic bed cyst, which frequently lacks distinguishable CT features from thymoma.

Management of incidental anterior mediastinal lesions: summary of relevant studies

With the increasing use of chest computed tomography (CT) imaging, the detection of asymptomatic incidental lesions in the anterior mediastinum has become more frequent. The prevalence of incidental nodular lesions in the anterior mediastinum is 0.49% to 0.89%. Most of these lesions manifest as soft tissue nodules measuring between 10 and 30 mm on non-contrast CT images. Thymic epithelial tumors are mainly responsible for larger lesions, while smaller lesions are primarily benign cysts. Most incidental thymic epithelial tumors are early-stage and have a favorable outcome. During follow-up, most lesions are stable, but some show indolent growth. Incidental lesions can be managed by a conservative patient-tailored approach with regular follow-up and the use of non-invasive imaging modalities such as magnetic resonance imaging.