To Be or Not to Be a Germ Cell: The Extragonadal Germ Cell Tumor Paradigm

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.

Histopathological, Demographic, and Clinical Signatures of Medulla Oblongata Germ Cell Tumors: A Case Report With the Review of Literature

The medulla oblongata is one of the rarest sites of occurrence for germ cell tumors (GCTs) of the central nervous system. As there is scant data regarding epidemiology, clinical presentations, optimal intervention, and long-term prognosis, we aimed to delineate the features of this rare entity by presenting our representative case and performing a quantitative review of the literature. A 24-year-old woman presented to our department with vertigo and swallowing difficulties. Magnetic resonance imaging revealed a homogenously enhanced exophytic lesion arising from the medulla oblongata and extending to the fourth ventricle. Surgical resection was performed and a histological diagnosis of pure germinoma was made. The patient underwent chemotherapy and whole-ventricular irradiation. No recurrence has been experienced for 4 months after the surgery. According to the literature, the prognosis of GCTs at the medulla oblongata seems no worse than those at typical sites. Striking features including occurrence at an older age, female preponderance, and a predominance of germinoma were noteworthy. The pattern of local recurrence suggests extensive radiation coverage is not a prerequisite. Special attention is needed for cardiac and respiratory functions as the main factors eliciting mortality.

Primary Pure Intrarenal Yolk Sac Tumor in 1.5-Year-Old Boy-A Rare Case Report

Germ cell tumors primarily arise in gonads and extragonadal germ cell tumors, an uncommon entity, originates usually along the midline. Here, we report the fifth example of intrarenal pure yolk sac tumor in a 1.5-year-old boy who presented with abdominal pain and underwent excision of the mass for suspected Wilms tumor. On histopathology and immunohistochemistry, a diagnosis of a yolk sac tumor was rendered. Postoperative serum alpha-fetoprotein levels were 21 000 ng/dl. The purpose of this report is to emphasize the importance of suspecting a germ cell tumor as one of the differential diagnoses of a suspected case of Wilms tumor and the significance of evaluating serum alpha-fetoprotein levels preoperatively.

A spontaneous ovarian teratoma in an FVB/n female mouse: Case report and literature review

Background

Teratomas are rare types of germ cell neoplasms composed of various differentiated or undifferentiated tissues.

Case Description

A 25-week-old female control FVB /n mouse in a 4-week toxicity study presented abdominal distension and poor body condition. It was euthanized, and the necropsy examination revealed a large mass connected to the tip of the right uterine horn, occupying the entire abdominal cavity. Microscopically, this mass showed areas of epidermal differentiation, with laminated keratin and sebaceous glands, differentiation into respiratory and digestive epithelium, cartilage, bone, and extensive areas of differentiation into the nervous tissue, being classified as an ovarian teratoma.

Conclusion

As far as authors know, the occurrence of ovarian teratomas in the FVB/n mouse strain has never been previously described.

Neuroimaging of pediatric tumors of the sellar region-A review in light of the 2021 WHO classification of tumors of the central nervous system

Sellar/suprasellar tumors comprise about 10% of all pediatric Central Nervous System (CNS) tumors and include a wide variety of entities, with different cellular origins and distinctive histological and radiological findings, demanding customized neuroimaging protocols for appropriate diagnosis and management. The 5th edition of the World Health Organization (WHO) classification of CNS tumors unprecedently incorporated both histologic and molecular alterations into a common diagnostic framework, with a great impact in tumor classification and grading. Based on the current understanding of the clinical, molecular, and morphological features of CNS neoplasms, there have been additions of new tumor types and modifications of existing ones in the latest WHO tumor classification. In the specific case of sellar/suprasellar tumors, changes include for example separation of adamantinomatous and papillary craniopharyngiomas, now classified as distinct tumor types. Nevertheless, although the current molecular landscape is the fundamental driving force to the new WHO CNS tumor classification, the imaging profile of sellar/suprasellar tumors remains largely unexplored, particularly in the pediatric population. In this review, we aim to provide an essential pathological update to better understand the way sellar/suprasellar tumors are currently classified, with a focus on the pediatric population. Furthermore, we intend to present the neuroimaging features that may assist in the differential diagnosis, surgical planning, adjuvant/neoadjuvant therapy, and follow-up of this group of tumors in children.

Clinical Challenges in the Management of Malignant Ovarian Germ Cell Tumours

Nonepithelial ovarian cancers (NEOC) are a group of rare malignancies, including germ cell tumours (GCT) and sex cord-stromal tumours (SCST), along with small-cell carcinomas and sarcomas. GCTs represent 2-5% of ovarian cancers, with a yearly incidence of 4:100,000, and they usually affect young women and adolescents. Precursory germ cells of the ovary form the basis of GCT. They are histologically classified into primitive GCT, teratomas, and monodermal and somatic-type tumours associated with dermoid cysts. A primitive GCT can be either a yolk sac tumour (YST), dysgerminoma, or mixed germ cell neoplasm. Teratomas are either mature (benign) or immature (malignant). Given that malignant GCTs occur rarely compared to epithelial ovarian tumours (EOC), greater focus is required in their diagnosis and treatment. In this article, we review the epidemiology, clinical manifestations, diagnosis, and molecular biology, along with the management and therapeutic challenges.

Once upon a Testis: The Tale of Cyclic Nucleotide Phosphodiesterase in Testicular Cancers

Phosphodiesterases are key regulators that fine tune the intracellular levels of cyclic nucleotides, given their ability to hydrolyze cAMP and cGMP. They are critical regulators of cAMP/cGMP-mediated signaling pathways, modulating their downstream biological effects such as gene expression, cell proliferation, cell-cycle regulation but also inflammation and metabolic function. Recently, mutations in PDE genes have been identified and linked to human genetic diseases and PDEs have been demonstrated to play a potential role in predisposition to several tumors, especially in cAMP-sensitive tissues. This review summarizes the current knowledge and most relevant findings regarding the expression and regulation of PDE families in the testis focusing on PDEs role in testicular cancer development.

Endocannabinoid system and epigenetics in spermatogenesis and testicular cancer

In mammals, male germ cell development starts during fetal life and is carried out in postnatal life with the formation of sperms. Spermatogenesis is the complex and highly orderly process during which a group of germ stem cells is set at birth, starts to differentiate at puberty. It proceeds through several stages: proliferation, differentiation, and morphogenesis and it is strictly regulated by a complex network of hormonal, autocrine and paracrine factors and it is associated with a unique epigenetic program. Altered epigenetic mechanisms or inability to respond to these factors can impair the correct process of germ development leading to reproductive disorders and/or testicular germ cell cancer. Among factors regulating spermatogenesis an emerging role is played by the endocannabinoid system (ECS). ECS is a complex system comprising endogenous cannabinoids (eCBs), their synthetic and degrading enzymes, and cannabinoid receptors. Mammalian male germ cells have a complete and active ECS which is modulated during spermatogenesis and that crucially regulates processes such as germ cell differentiation and sperm functions. Recently, cannabinoid receptor signaling has been reported to induce epigenetic modifications such as DNA methylation, histone modifications and miRNA expression. Epigenetic modifications may also affect the expression and function of ECS elements, highlighting the establishment of a complex mutual interaction. Here, we describe the developmental origin and differentiation of male germ cells and testicular germ cell tumors (TGCTs) focusing on the interplay between ECS and epigenetic mechanisms involved in these processes.

Histogenesis of intracranial germ cell tumors: primordial germ cell vs. embryonic stem cell

INTRODUCTION

Intracranial germ cell tumor (iGCT) is a rare disorder and often occurs during childhood and adolescence. iGCTs are frequently localized in pineal region and hypothalamic-neurohypophyseal axis (HNA). In spite of well-established clinical and pathological entity, histogenesis of iGCTs remains unsettled. Current theories of histogenesis of iGCTs include germ cell theory (from primordial germ cells (PGCs) of aberrant migration) and stem cell theory (transformed embryonic stem (ES) cells). In order to comprehend the histogenesis, we revisit the origin, migration, and fate of the human PGCs, and their transformation processes to iGCT.

DISCUSSION

In "germ cell theory," transformation of ectopic PGCs to iGCT is complex and involves multiple transcription factors. Germinoma is derived from ectopic PGCs and is considered a prototype of all GCTs. Non-germinomatous germ cell tumors (NGGCTs) develop from more differentiated counterparts of embryonic and extra-embryonic tissues. However, there is a distinct genomic/epigenomic landscape between germinoma and NGGCT. ES cells transformed from ectopic PGCs through molecular dysregulation or de-differentiation may become the source of iGCT. "Stem cell theory" is transformation of endogenous ES cells or primitive neural stem cell to iGCTs. It supports histological diversity of NGGCTs because of ES cell's pluripotency. However, neural stem cells are abundantly present along the subependymal zone; therefore, it does not explain why iGCTs almost exclusively occur in pineal and HNA locations. Also, the vast difference of methylation status between germinoma and NGGCT makes it difficult to theorize all iGCTs derive from the common cellular linage.

CONCLUSION

Transformation of PGCs to ES cells is the most logical mechanism for histogenesis of iGCT. However, its detail remains an enigma and needs further investigations.

Genomic features of mediastinal germ cell tumors: a narrative review

BACKGROUND AND OBJECTIVE

Germ cell tumors (GCTs) are uncommon malignancies generally originating from gonads. However, about 5% of GCTs arise outside the gonad (extragonadal), of which 80% develop from the mediastinum. While the prognosis of seminomas is not affected by the gonadal or extragonadal primary location, the prognosis of nonseminoma primary mediastinal GCTs (NS-PMGCTs) is poor, compared to its gonadal counterpart with an estimated 5-year overall survival of about 50%. The current treatments are sub-optimal to increase the cure rate of these rare GCTs. Therefore, molecular insights into these tumors would be valuable to develop novel therapies. The main objective of this review is to describe and dissect the genomic features associated with primary mediastinal GCTs (PMGCTs), highlighting the more frequent genomic alterations and their correlation with clinical outcomes.

METHODS

We conducted a narrative review of the English literature available in PubMed and Google Scholar between 1982 and 2021, including meta-analyses, systematic reviews, case series and case reports regarding the genomic and clinical features of PMGCTs. We analyzed the available data to describe the molecular characteristics of PMGCTs compared to testicular GCTs (TGCTs), highlighting the most relevant biological and prognostic factors.

KEY CONTENT AND FINDINGS

The high percentage of platinum resistance, the unique association with hematologic malignancies (HMs) and other malignancies, the higher prevalence of P53 mutations, and a distinct genomic landscape characterize this rare disease.

CONCLUSIONS

Although some studies have unveiled recurrent molecular alterations in PMGCTs, few are particularly suitable for targeted therapy. Due to the rarity of PMGCTs, data sharing and the creation of an international consortium would be helpful to have a better understanding of the molecular drivers of these tumors.

Stay on the road: from germ cell specification to gonadal colonization in mammals

The founder cells of the gametes are primordial germ cells (PGCs). In mammals, PGCs are specified early during embryonic development, at the boundary between embryonic and extraembryonic tissue, long before their later residences, the gonads, have developed. Despite the differences in form and behaviour when differentiated into oocytes or sperm cells, in the period between specification and gonadal colonization, male and female PGCs are morphologically indistinct and largely regulated by similar mechanisms. Here, we compare different modes and mechanisms that lead to the formation of PGCs, putting in context protocols that are in place to differentiate both human and mouse pluripotent stem cells into PGC-like cells. In addition, we review important aspects of the migration of PGCs to the gonadal ridges, where they undergo further sex-specific differentiation. Defects in migration need to be effectively corrected, as misplaced PGCs can become tumorigenic. Concluding, a combination of in vivo studies and the development of adequate innovative in vitro models, ensuring both robustness and standardization, are providing us with the tools for a greater understanding of the first steps of gametogenesis and to develop disease models to study the origin of germ cell tumours.

This article is part of the theme issue ‘Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom’.

Extragonadal Germ Cell Tumors of the Mediastinum and Retroperitoneum: A Surveillance, Epidemiology, and End Results-based Study

OBJECTIVES

Extragonadal germ cell tumors (EGCT) are a rare entity, most of them being located in the mediastinum and retroperitoneum. Information on these tumors is scarce, requiring carrying out large population-based studies to better understand these diseases. We aimed to determine the clinical features and prognosis of patients with EGCT of the mediastinum and retroperitoneum.

MATERIALS AND METHODS

Demographic and clinicopathological features of patients diagnosed with EGCT of the mediastinum and retroperitoneum from 1975 to 2016 were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database.

RESULTS

A total of 1674 patients were included, 1297 (77.5%) of mediastinal origin and 377 (22.5%) of retroperitoneum. Nonseminomatous tumors (56.3%) were slightly more frequent than seminomas (43.7%) with similar distribution between mediastinum and retroperitoneum. After a median follow-up of 137 months, the median overall survival was 263 months (95% CI, 220-296) whereas the median cause-specific survival (CSS) has still not been reached. The 10-year overall survival and CSS were 57.4% (95% CI, 55-59.7) and 63% (95% CI, 60.6-65.2) respectively. Multivariate analysis showed that older age, mediastinal location, nonseminomatous histology, and distant disease at diagnosis were independent prognostic factors correlated with a worse prognosis. Patients with mediastinal choriocarcinoma and embryonal carcinoma have the worst prognosis, both with a median CSS of only 12 months.

CONCLUSIONS

Despite a decreasing incidence observed in recent decades, EGCT continues to represent a challenge for oncologists. The prognosis of choriocarcinoma and embryonal carcinoma of the mediastinum remains poor and treatment strategies need to be improved urgently.

Case report: Mature extragonadal teratoma at the proximal part of the tail in a kitten

An 8-month-old, intact male, domestic shorthair cat was referred for a mass on the proximal ventral part of the tail which had been found since the animal was born, and due to the presence of a linear fissure with rows of ectopic teeth, the veterinarian suspected that the mass had recently ruptured. Tail amputation was elected and the entire mass was successfully surgically excised. From the gross examination, this mass had an open cyst-like structure with a prominent area composed of hair, teeth, and bone. Histopathology revealed two components of germinal layers including hair follicles, adnexal tissue, neural tissue, teeth, muscle, fat, bone, and lymphatic vessels. The histopathological diagnosis was consistent to mature teratoma. Although, complete excision could not be definitively confirmed histologically, this kitten is currently well and has not developed any recurrent mass at the surgical site after 2 years of post-operation.

Endodermal sinus tumor with pancreatic origin: A case report

Endodermal Sinus tumor is a rare malignant type of germ cell tumor (GCT). Primary endodermal sinus tumor, especially in the head of pancreas, is extremely rare. The case under consideration is of a 22 year old male who presented with pancreatic mass causing postprandial nausea and vomiting, and raised AFP levels. The biopsy of the mass revealed the endodermal sinus tumor, and the pancreatic origin was confirmed by a CT scan and a negative scrotal ultrasound. As the tumor was unresectable initially, a gastrojejunostomy was done to relieve the obstructive symptoms. Whipple procedure was performed two months after 4 cycles of BEP chemotherapy to remove the residual tumor in pancreas. It is crucial to highlight this uncommon case in order to increase surgeons' and oncologists' knowledge of the malignant extra-gonadal GCTs diagnosis and treatment.

Germline stem cells in human

The germline cells are essential for the propagation of human beings, thus essential for the survival of mankind. The germline stem cells, as a unique cell type, generate various states of germ stem cells and then differentiate into specialized cells, spermatozoa and ova, for producing offspring, while self-renew to generate more stem cells. Abnormal development of germline stem cells often causes severe diseases in humans, including infertility and cancer. Primordial germ cells (PGCs) first emerge during early embryonic development, migrate into the gentile ridge, and then join in the formation of gonads. In males, they differentiate into spermatogonial stem cells, which give rise to spermatozoa via meiosis from the onset of puberty, while in females, the female germline stem cells (FGSCs) retain stemness in the ovary and initiate meiosis to generate oocytes. Primordial germ cell-like cells (PGCLCs) can be induced in vitro from embryonic stem cells or induced pluripotent stem cells. In this review, we focus on current advances in these embryonic and adult germline stem cells, and the induced PGCLCs in humans, provide an overview of molecular mechanisms underlying the development and differentiation of the germline stem cells and outline their physiological functions, pathological implications, and clinical applications.

Socio-behavioral dysfunction in disorders of hypothalamic-pituitary involvement: The potential role of disease-induced oxytocin and vasopressin signaling deficits

Disorders involving hypothalamic and pituitary (HPIT) structures-including craniopharyngioma, Langerhans cell histiocytosis, and intracranial germ cell tumors-can disrupt brain and endocrine function. An area of emerging clinical concern in patients with these disorders is the co-occurring socio-behavioral dysfunction that persists after standard hormone replacement therapy. Although the two neuropeptides most implicated in mammalian social functioning (oxytocin and arginine vasopressin) are of hypothalamic origin, little is known about how disease-induced damage to HPIT structures may disrupt neuropeptide signaling and, in turn, impact patients' socio-behavioral functioning. Here we provide a clinical primer on disorders of HPIT involvement and a review of neuropeptide signaling and socio-behavioral functioning in relevant animal models and patient populations. This collective evidence suggests that neuropeptide signaling disruptions contribute to socio-behavioral deficits experienced by patients with disorders of HPIT involvement. A better understanding of the biological underpinnings of patients' socio-behavioral symptoms is now needed to enable the development of the first targeted pharmacological strategies by which to manage patients' socio-behavioral dysfunction.

Mapk activation drives male and female mouse teratocarcinomas from late PGCs

Germ cell tumors (GCTs) are rare tumors that can develop in both sexes, peaking in adolescents. To understand the mechanisms that underlie germ cell transformation, we established a GCT mouse model carrying germ cell-specific BRafV600E mutation with or without heterozygous Pten deletion. Both male and female mice developed monolateral teratocarcinomas containing embryonal carcinoma (EC) cells that showed an aggressive phenotype and metastatic ability. Germ cell transformation started in fetal gonads and progressed after birth leading to gonadal invasion. Early postnatal testes showed foci of tumor transformation, while ovaries showed increased number of follicles, multi-ovular follicles (MOFs) and scattered metaphase I oocytes containing follicles. Our results indicate that Mapk over-activation in fetal germ cells of both sexes can expand their proliferative window leading to neoplastic transformation and metastatic behavior.

Retroperitoneal extragonadal germ cell tumor with duodenal infiltration: A challenging endo‐luminal tissue diagnosis

A 32‐year‐old Malay male was referred to our hospital for a second opinion. An abdominal and pelvic CT scan at the previous medical facility showed a large retroperitoneal tumor, which was subjected to ultrasound‐guided fine‐needle aspiration cytology (FNAC) with a provisional diagnosis of malignant lymphoma. However, after reviewing the existing results, a repeat biopsy was deemed necessary and this was performed endoluminally via gastroduodenoscopy in view of the close proximity of the tumor and the third part of the duodenum. The first biopsy failed to detect any abnormal cells, but a repeat biopsy with supporting evidence from other laboratory results led to a final diagnosis of extragonadal germ cell tumor (GCT) with duodenal infiltration.

PI3K/PTEN/AKT Signaling Pathways in Germ Cell Development and Their Involvement in Germ Cell Tumors and Ovarian Dysfunctions

Several studies indicate that the PI3K/PTEN/AKT signaling pathways are critical regulators of ovarian function including the formation of the germ cell precursors, termed primordial germ cells, and the follicular pool maintenance. This article reviews the current state of knowledge of the functional role of the PI3K/PTEN/AKT pathways during primordial germ cell development and the dynamics of the ovarian primordial follicle reserve and how dysregulation of these signaling pathways may contribute to the development of some types of germ cell tumors and ovarian dysfunctions.

Treatment and Survival of Malignant Extracranial Germ Cell Tumours in the Paediatric Population: A Systematic Review and Meta-Analysis

OBJECTIVE

This systematic review and meta-analysis was performed to explore overall survival (OS) and event free survival (EFS) rates internationally over the past two decades and to define specific subgroups with inferior outcomes which may demand different treatment strategies.

METHODS

The search focused on malignant extracranial germ cell tumours (GCTs) in the paediatric population. The initial database search identified 12,556 articles; 32 articles were finally included in this review, comprising a total of 5095 patients.

RESULTS

The studies were heterogeneous, varying from single institution reports to large prospective trials. Older studies, describing eras where non-platinum-based chemotherapy regimens were used, showed clearly worse outcomes. Survival for stage I-II gonadal disease is excellent. On the other hand, patients with an initial alpha-fetoprotein (AFP) > 10,000 ng/mL or kU/L, age > 11 years and stage IV disease confer a survival disadvantage. For testicular disease in particular, lymphovascular invasion and certain histopathological subtypes, such as embryonal carcinoma (EC) and mixed malignant GCTs, survival is poorer. Survival data for sacrococcygeal and mediastinal GCTs show a heterogeneous distribution across studies in this review, independent of year of publication. Patients > 12 years presenting with a mediastinal GCT pose a subpopulation which fares worse than GCTs in other locations or age groups. This is independent of AFP levels, stage of disease or treatment protocol, and these patients may demand a different treatment strategy.

CONCLUSIONS

This review describes the heterogeneous nature of GCTs in different anatomical locations, impacting on stage at presentation, treatment modalities used and survival data. Despite this heterogeneity, in line with the current developmental biology-based classification system, subpopulations can be defined which have an inferior EFS and OS and where future research and more individualised treatment would help to improve survival.