Primary Mediastinal Germ Cell Tumors: A Thorough Literature Review

Micronodular thymic epithelial tumors with lymphoid hyperplasia and mimicking lesions

Micronodular arrangement of epithelial cells and lymphoid B-cell hyperplasia with follicles are both peculiar histological features in thymic tissue. Such features may especially occur in thymic epithelial tumors. The most common form is called micronodular thymoma with lymphoid stroma. We have recently described some characteristics of thymic micronodular carcinoma with lymphoid hyperplasia, highlighting how this carcinomatous counterpart should not be misdiagnosed as a thymoma. In this review, we discuss these two entities but also other mimics, which may occur in the anterior mediastinum. These mimics include various types of cellular micronodules and lymphoid backgrounds encompassing a wide range of mediastinal lesions. Non-neoplastic lesions, such as thymic nodular epithelial hyperplasia, thymic lymphoid hyperplasia, or sarcoidosis, as well as tumors of very varying aggressiveness, such as micronodular thymic epithelial tumors, low-grade lymphoma, seminoma, or lymphoepithelial carcinoma, are discussed. We show how these lesions may be misleading and we describe how a correct diagnostic may be obtained in current practice.

Optimal Treatment Strategies for Early-Stage Primary Mediastinal Germ Cell Tumors

BACKGROUND

Data on optimal therapy for patients with primary mediastinal germ cell tumors consist primarily of single-institution studies with small sample sizes. The objective of this study was to assess the association of survival outcomes with surgery vs nonoperative management for patients with early-stage primary mediastinal germ cell tumors.

METHODS

Overall survival of all patients with seminomas and nonseminomatous primary germ cell tumors in the mediastinum who received (1) chemotherapy, or (2) surgery with or without chemotherapy (hereafter referred to as the "surgery" group) for early-stage disease from 2004 to 2015 in the National Cancer Database was assessed by Kaplan-Meier analysis, propensity score-matched analysis, and multivariable Cox proportional hazards analysis.

RESULTS

For patients with seminomas, chemotherapy alone was used in 120 (80.5%) patients and surgery was used in 29 (19.5%) patients. There was no significant difference in 5-year survival between surgery and chemotherapy in unadjusted and propensity score-matched analysis. For patients with nonseminomatous tumors, chemotherapy alone was used in 91 (46.7%) patients and surgery was used in 104 (53.3%) patients. Surgery was associated with improved 5-year survival compared with chemotherapy in unadjusted, multivariable-adjusted, and propensity score-matched analysis.

CONCLUSIONS

In this national analysis, multimodality treatment involving surgery was associated with improved survival compared with chemotherapy alone for early-stage primary mediastinal nonseminomatous germ cell tumors. For seminomas of the mediastinum, chemotherapy was associated with similar long-term outcomes compared with multimodality treatment involving surgery.

Current Trends in the Surgical Management of Yolk Sac Tumors

Mediastinal yolk sac tumors (YST) constitute a highly malignant subtype of primary non-seminomatous germ cell tumors, which are often locally advanced and unresectable at diagnosis. Due to their rarity and aggressiveness, there is not yet a standard optimal treatment approach. A widely employed multimodal strategy involves neoadjuvant cisplatin-based combination chemotherapy followed by consolidation surgery. Tumor infiltration into the lungs and adjacent cardiovascular structures is common, such that surgical intervention typically requires extensive resections, performed either by sternotomy or thoracotomy. For this review, we extensively searched the PubMed and Embase medical databases, identifying articles describing surgical treatment of mediastinal yolk sac tumors. The current literature provides limited details regarding the utilized surgical procedures, leaving clinicians without comprehensive guidance about the demanding nature of these resections. Here, we present a narrative description of the range of current surgical procedures. By highlighting these techniques, we provide a comprehensive overview of the current surgical landscape, thereby helping clinicians understand the potential complexities and considerations involved in managing these rare and aggressive tumors.

SEOM-GG clinical guidelines for the management of germ-cell testicular cancer (2023)

Testicular germ cell tumors are the most common tumors in adolescent and young men. They are curable malignancies that should be treated with curative intent, minimizing acute and long-term side effects. Inguinal orchiectomy is the main diagnostic procedure, and is also curative for most localized tumors, while patients with unfavorable risk factors for recurrence, or those who are unable or unwilling to undergo close follow-up, may require adjuvant treatment. Patients with persistent markers after orchiectomy or advanced disease at diagnosis should be staged and classified according to the IGCCCG prognostic classification. BEP is the most recommended chemotherapy, but other schedules such as EP or VIP may be used to avoid bleomycin in some patients. Efforts should be made to avoid unnecessary delays and dose reductions wherever possible. Insufficient marker decline after each cycle is associated with poor prognosis. Management of residual masses after chemotherapy differs between patients with seminoma and non-seminoma tumors. Patients at high risk of relapse, those with refractory tumors, or those who relapse after chemotherapy should be managed by multidisciplinary teams in experienced centers. Salvage treatment for these patients includes conventional-dose chemotherapy (TIP) and/or high-dose chemotherapy, although the best regimen and strategy for each subgroup of patients is not yet well established. In late recurrences, early complete surgical resection should be performed when feasible. Given the high cure rate of TGCT, oncologists should work with patients to prevent and identify potential long-term side effects of the treatment. The above recommendations also apply to extragonadal retroperitoneal and mediastinal tumors.

Metastatic epidural spinal cord compression from testicular yolk sac tumor: case report and literature review

Background

Yolk sac tumor (YST), or endodermal sinus tumor, is classically associated with pediatric populations. Metastasis to the spine rarely occurs, usually involving the lower thoracic or lumbar vertebrae. The objective of this report is to present a rare case of YST metastasis to the lower cervical and upper thoracic vertebrae in an adult male. A case-based review of the literature on metastatic YSTs was also performed as an update to the relevant literature.

Case Description

A 28-year-old male with a history of YST presented to our institution with urinary retention, increasing weakness in the upper extremities, and acute onset lower extremity weakness. Computed tomography (CT) and magnetic resonance imaging (MRI) scans confirmed evidence of metastasis from a known YST with symptomatic cord compression. The patient was treated with surgical excision via decompressive laminectomies with instrumentation as described, and histopathologic analysis of the specimen confirmed YST metastasis. His disease recurred one year after index surgery. He succumbed to his disease despite repeated debulking.

Conclusions

Metastasis of YST is rare, but metastasis to lower cervical and upper thoracic vertebrae is possible. YSTs are usually treated via primary surgical resection. Systemic chemotherapy and radiation may prevent recurrence. However, individualized treatment is imperative for improved patient outcomes.

Teratoma to Angiosarcoma: A Metamorphosis in the Mediastinum

We describe a rare and remarkable transformation of an immature mediastinal teratoma into high-grade angiosarcoma in a 21-year-old male. Mediastinal teratomas, particularly immature ones, are exceedingly rare, representing a small fraction of germ cell tumors (GCTs). Our case describes the clinical journey of the patient, who initially presented with acute chest pain and was subsequently diagnosed with an immature teratoma following imaging studies and elevated tumor markers. Despite an initial positive response to cisplatin-based chemotherapy, surveillance imaging revealed liver masses, which a biopsy confirmed as angiosarcoma. This transformation underscores the aggressive nature of immature teratomas and the propensity for sarcomatous differentiation, particularly in the mediastinum. The case contributes valuable insight into the management and surveillance of mediastinal non-seminoma germ cell tumors (MNGCT), a subset of GCTs with limited literature. We believe this case is the first in the literature to describe a transformation from an immature teratoma in the mediastinum to a high-grade angiosarcoma.

Primary mediastinal seminoma with azoospermia: case report and review of the literature

Introduction

Since the first report, primary mediastinal seminoma has a low incidence in the population, and it mainly affects young and middle-aged men, is clinically rare, and accounts for a very small proportion of mediastinal tumors. In this study, we describe the first case of primary mediastinal seminoma with azoospermia and hypothesize that the coexistence of the two disorders may not be a coincidence.

Case report

A 16-year-old man presented with chest tightness and chest pain, a mediastinal mass on chest CT, and abnormal 18F-fluoro-deoxyglucose uptake on a PET-CT scan. By biopsy of the mass, the pathological diagnosis was a primary mediastinal seminoma. Because chemotherapy is included in the treatment of the tumor, the patient underwent sperm freezing before treatment, considering that chemotherapy can affect fertility, but the patient was diagnosed with azoospermia. Finally, the patient underwent tumor resection and postoperative chemotherapy. No tumor recurrence was observed at the current follow-up.

Conclusion

Primary mediastinal seminoma is mainly confirmed by histopathological examination, and surgery and chemoradiotherapy are the current treatments. In patients with mediastinal seminoma or azoospermia, doctors should be aware that the two disorders may coexist, especially in men who have fertility requirements or long-term infertility, and that examination of the mediastinum and semen may lead to unexpected findings in the diagnosis and treatment. For mediastinal germ cell tumors, genetic testing is of great value in the treatment of tumors and the prediction of associated diseases. Future studies exploring the potential correlation between mediastinal seminoma and azoospermia will be prospective.

Survival difference among adult and pediatric mediastinal yolk sac tumors cases: A meta-analysis of case reports

BACKGROUND

Mediastinal Yolk sac tumors (YST) are rare and highly malignant extragonadal germ cell tumors with rapid growth and early metastases. We sought to conduct a meta-analysis of published case reports/case series to compare differences in survival, demographics, and treatment modalities between adult and pediatric patients with YST.

METHODS

Ovid Embase, Cochrane, and Ovid Medline databases were searched for primary mediastinal pure YST cases. The primary outcome was overall survival (OS). Log-rank and Cox regression were used. This study is registered on PROSPERO (CRD42022367586).

RESULTS

Among 846 studies, 87 met our inclusion criteria including 130 patients (Adults: 90 and Pediatrics: 40). About 41.5% of the patients were from the United States. The median age was 23.0 (Q1-Q3: 17.0-30.0), 88.5% were males, and (32.3%) were Asian. Stage II represented almost 40%. AFP was elevated in 96.9%. Respiratory distress was the presenting symptom in 65.4%. Chemotherapy, radiotherapy, and surgery were utilized in 84.6, 23.1, and 64.7% respectively. Median OS was 24 months (Adults: 23 months, Pediatrics: 25 months, P = 0.89). 3- and 5-year OS were 34.4% and 22.9% in adults and 41.5% and 41.5% in pediatrics, respectively. On multivariate analysis, anterior location of tumors, receipt of chemotherapy, and undergoing surgery were associated with better OS.

CONCLUSION

Primary mediastinal YSTs are rare, but lethal neoplasms. Our meta-analysis showed that mediastinal YSTs mimic other non-seminomatous mediastinal GCTs in terms of clinical characteristics and available treatment options. Early diagnosis, neoadjuvant chemotherapy, and surgical resection are the key points for effective management and improved outcomes.

The combination of maximum standardized uptake value and clinical parameters for improving the accuracy in distinguishing primary mediastinal lymphomas from thymic epithelial tumors

Background

Anterior mediastinal masses are relatively uncommon, and mediastinal lymphomas are the malignancies most likely to be confused with thymic epithelial tumors (TETs). The aim of this study was to investigate whether the combination of 18fluorine-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET-CT) findings and clinical parameters is useful in differentiating lymphoma from TETs in anterior mediastinal masses.

Methods

This retrospective study consecutively included 304 patients with anterior mediastinal masses (244 TETs and 60 lymphomas) who underwent 18F-FDG PET-CT 1 to 2 weeks before tumor resection or biopsy between August 2016 and March 2022. The correlations between the maximum standardized uptake value (SUVmax) of tumors and clinical parameters of patients with histology subtypes were analyzed. Receiver operating characteristic curve analysis was used to obtain the optimal cutoff values of age, lactate dehydrogenase (LDH), tumor size, and SUVmax to predict lymphoma. Logistic regression analysis was used to identify potential predictive factors for lymphoma.

Results

Lymphoma was significantly associated with younger patient age, higher LDH level, larger tumor size, and higher SUVmax compared to TETs (P<0.001). In the modeling cohort, age ≤40.5 years, LDH level ≥197 U/L, tumor size ≥10.72 cm, and SUVmax ≥11.95 were identified as independent predictors for lymphoma with odds ratios of 20.14 [95% confidence interval (CI): 6.02-67.40; P<0.001], 4.89 (95% CI: 1.27-18.89; P=0.021), 8.82 (95% CI: 2.31-33.69; P=0.001), and 30.01 (95% CI: 6.59-136.72; P<0.001), respectively. The accuracy of age, LDH, tumor size, and SUVmax in predicting lymphoma was 84.8%, 67.8%, 85.2%, and 78.3% respectively. The combination of the four above parameters could improve the predictive accuracy to 89.1%, and in the validation cohort, this combination increased the predictive accuracy to 87.8%.

Conclusions

SUVmax on 18F-FDG PET-CT has the potential ability to discriminate lymphomas from TETs in the diagnosis of anterior mediastinal masses, and the combination of SUVmax with clinical parameters can improve the diagnostic accuracy. This combination may therefore may be helpful in avoiding unnecessary operation in patients with anterior mediastinal lymphomas.

Machine learning-based CT texture analysis in the differentiation of testicular masses

Purpose

To evaluate the ability of texture features for distinguishing between benign and malignant testicular masses, and furthermore, for identifying primary testicular lymphoma in malignant tumors and identifying seminoma in testicular germ cell tumors, respectively.

Methods

We retrospectively collected 77 patients with an abdominal and pelvic enhanced computed tomography (CT) examination and a histopathologically confirmed testicular mass from a single center. The ROI of each mass was split into two parts by the largest cross-sectional slice and deemed to be two samples. After all processing steps, three-dimensional texture features were extracted from unenhanced and contrast-enhanced CT images. Excellent reproducibility of texture features was defined as intra-class correlation coefficient ≥0.8 (ICC ≥0.8). All the groups were balanced via the synthetic minority over-sampling technique (SMOTE) method. Dimension reduction was based on pearson correlation coefficient (PCC). Before model building, minimum-redundancy maximum-relevance (mRMR) selection and recursive feature elimination (RFE) were used for further feature selection. At last, three ML classifiers with the highest cross validation with 5-fold were selected: autoencoder (AE), support vector machine(SVM), linear discriminant analysis (LAD). Logistics regression (LR) and LR-LASSO were also constructed to compare with the ML classifiers.

Results

985 texture features with ICC ≥0.8 were extracted for further feature selection process. With the highest AUC of 0.946 (P <0.01), logistics regression was proved to be the best model for the identification of benign or malignant testicular masses. Besides, LR also had the best performance in identifying primary testicular lymphoma in malignant testicular tumors and in identifying seminoma in testicular germ cell tumors, with the AUC of 0.982 (P <0.01) and 0.928 (P <0.01), respectively.

Conclusion

Until now, this is the first study that applied CT texture analysis (CTTA) to assess the heterogeneity of testicular tumors. LR model based on CTTA might be a promising non-invasive tool for the diagnosis and differentiation of testicular masses. The accurate diagnosis of testicular masses would assist urologists in correct preoperative and perioperative decision making.