Mediastinal germ cell tumors: a narrative review of their traits and aggressiveness features

Perioperative strategies and management of giant anterior mediastinal tumors: a narrative review

Background and Objective

Giant anterior mediastinal tumors sometimes may cause circulatory collapse and respiratory failure, known as mediastinal mass syndrome (MMS). The prediction and prevention of MMS is challenging. The aim of this study is to summarize the evaluation methods for MMS and formulate treatment strategies for giant anterior mediastinal tumors.

Methods

We performed a thorough analysis of recent international literature on giant anterior mediastinal tumors (>10 cm in diameter) and MMS published in the PubMed database. The search spanned the duration of the preceding 10 years from August 19, 2023, and only studies published in English were included.

Key Content and Findings

Mature teratomas and liposarcomas are the most common giant anterior mediastinal tumors and MMS develops most frequently in case of malignant lymphomas. Here, we propose a new treatment strategy for giant anterior mediastinal tumors. Based on imaging findings, giant anterior mediastinal tumors can be classified as cystic or solid and further blood investigation data are useful for a definitive diagnosis. When malignant lymphoma or malignant germ cell tumor is highly suspected, the first choice of treatment is not surgery but chemotherapy and radiotherapy. Moreover, image-guided drainage may be effective if giant cystic anterior tumors develop into MMS. The risk classification of MMS is important for treating giant anterior mediastinal tumors. If the MMS risk classification is 'unsafe' or 'uncertain', the intraoperative management deserves special attention. The surgical approach should however be based on tumor localization and invasion of surrounding tissues. Multidisciplinary team coordination is indispensable in the treatment of giant anterior mediastinal tumors.

Conclusions

When giant anterior mediastinal tumors are encountered, it is important to follow the appropriate treatment strategy, focusing on the development of MMS based on imaging findings and symptoms.

Primary germ cell tumours of the mediastinum: A review with emphasis on diagnostic challenges

This article will review current aspects of the histopathological, immunohistochemical and molecular analysis of primary mediastinal germ cell tumours (PMGCTs) as well as their aetiological, epidemiological, clinical and therapeutic features. PMGCTs represent an important differential diagnosis in the spectrum of mediastinal tumours, and their diagnosis is usually made on small tissue samples from core needle biopsies in combination with diagnostic imaging and serum tumour markers. As in lymphomas, a small biopsy is often the only viable tumour sample available from these patients, as they receive chemotherapy prior to eventual surgical resection. Pathologists therefore need to apply an efficient combination of immunohistochemical markers to confirm the diagnosis of a PMGCT and to exclude morphological mimics.

Approach to Imaging of Mediastinal Masses

Mediastinal masses present a diagnostic challenge due to their diverse etiologies. Accurate localization and internal characteristics of the mass are the two most important factors to narrow the differential diagnosis or provide a specific diagnosis. The International Thymic Malignancy Interest Group (ITMIG) classification is the standard classification system used to localize mediastinal masses. Computed tomography (CT) and magnetic resonance imaging (MRI) are the two most commonly used imaging modalities for characterization of the mediastinal masses.

Primary mediastinal seminoma presenting with paraneoplastic anti-Hu encephalitis: a case report and literature review

Primary mediastinal seminomas are exceedingly rare tumors, often localized to the anterior mediastinum. They may present with numerous complications, including superior vena cava syndrome, chylothorax, and pericardial effusions. Less commonly, they may present with paraneoplastic encephalitis. In this report we describe a case of a 19-year-old male with no significant past medical history who presented with bilateral hearing loss, progressive neuropathy, and ataxia. Subsequently the patient was found to have mediastinal mass with a high-titer anti-Hu antibody. To our knowledge, only one other case of mediastinal seminoma presenting with anti-Hu antibodies has been described in the literature. In this report, we describe a rare case of mediastinal seminoma, describe treatment options, and discuss additional known cases presenting with paraneoplastic encephalitis.

Genomic profiling of a metastatic anaplastic melanocytic neuroectodermal tumor arising from a mature thymic teratoma as part of a mediastinal germ cell tumor

Following chemotherapy, a mediastinal germ cell tumor can lead to a mature teratoma that is composed of tissues derived from all three germ layers. Although teratoma is usually curable, in rare cases it can give rise to various somatic tumors and exceptionally it undergoes melanocytic neuroectodermal tumor (MNT) transformation, a process that is not well-described. We report a patient with a postchemotherapy thymic teratoma associated with an MNT component who, 10 years later, additionally presented a vertebral metastasis corresponding to an anaplastic MNT. Using exome sequencing of the mature teratoma, the MNT and its metastatic vertebral anaplastic MNT components, we identified 19 somatic mutations shared by at least two components. Six mutations were common to all three components, and three of them were located in the known cancer-related genes KRAS (p.E63K), TP53 (p.P222X), and POLQ (p.S447P). Gene set enrichment analysis revealed that the melanoma tumorigenesis pathway was enriched in mutated genes including the four major driver genes KRAS, TP53, ERBB4, and KDR, indicating that these genes may be involved in the development of the anaplastic MNT transformation of the teratoma. To our knowledge, this is the first molecular study realized on MNT. Understanding the clinicopathological and molecular characteristics of these tumors is essential to better understand their development and to improve therapeutics.