Somatic-type malignancies in testicular germ cell tumors

MicroRNA-371-373 cluster and methylome analysis suggests that a subset of 'somatic-type' malignancies arising in germ cell tumors may originate in yolk sac tumor components

Somatic-type malignancies (SMs) arising in germ cell tumors (GCTs) are aggressive neoplasms resistant to systemic treatment. Most are diagnosed in metastatic sites after chemotherapy; however, they have also been well-documented in primary testicular GCTs. Historically, SMs were thought to originate in components of teratoma that acquire molecular alterations equivalent to those that characterize their true somatic counterparts. However, recent studies have shown that SMs typically lack the hallmark molecular alterations seen in similar somatic tumors. Additionally, clinicopathologic and molecular data suggest that a subset may derive from yolk sac tumor (YST) rather than teratoma. In this study, we evaluated the relationship between conventional histological types of GCTs and SMs by comparing expression of microRNA (miR)-371-373 and genomic methylation profiles. A total of 96 samples (including multiple paired conventional GCT-SM samples from individual tumors) were assessed for miR-371-373 expression by RT-qPCR and genomic DNA methylation using a clinically validated assay. Expression of miR-371-373 was higher in conventional GCTs than in SMs (considered as a single category encompassing all histological subtypes). However, miR-371-373 expression was heterogeneous among SMs, with significantly higher levels in sarcomatoid YST (SYST) and glandular neoplasms than in other SMs. Genomic DNA methylation analysis showed that SMs (considered as a single category) did not form a distinct cluster. Instead, they grouped into multiple clusters that did not show perfect correspondence with histology and often included conventional GCTs. Genome-wide methylation assessment showed a higher abundance of hypermethylated regions in SMs than in conventional GCTs. Analysis of paired conventional GCT and 'somatic-type' components that did not meet size criteria for SMs dissected from individual tumors demonstrated separation according to histology, suggesting that epigenetic processes play a role in the transition from conventional GCT to 'somatic-type' phenotypes. Gene-level and pathway-level analyses identified MAPK/RAS signaling, mitosis/proliferation, differentiation towards neural tissue/neuroectoderm, epithelial-to-mesenchymal transition, and DNA repair as key differentially regulated processes in components with somatic-type histology, suggesting mechanisms of progression from conventional to 'somatic' phenotypes in GCT. These results support the hypothesis that a subset of SMs derive from YST and suggest that some subtypes (such as SYST) may represent 'intermediate' phenotypes. Additionally, analysis of differentially methylated promoter regions in SM identified genes and biologic processess that may underlie 'somatic tranformation' in GCTs. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Molecular Diversity of Embryonic-Type Neuroectodermal Tumors Arising From Testicular Germ Cell Tumors

Embryonic-type neuroectodermal tumors (ENTs) arising from testicular germ cell tumors (GCTs) are a relatively common type of somatic transformation in GCTs with poor prognosis and limited therapeutic options, particularly when patients develop disease recurrence or metastasis. Knowledge of key events driving this transformation is limited to the paucity of comprehensive genomic data. We performed a retrospective database search in a Clinical Laboratory Improvement Amendments- and College of American Pathologists-certified laboratory for testicular GCT-derived ENTs that had previously undergone next-generation sequencing-based comprehensive genomic profiling during the course of clinical care. Clinicopathological and genomic data were centrally rereviewed. Here, we report the molecular features of 10 ENTs of testicular GCT origin. All tumors harbored gain of chromosome 12p, often with KRAS, CCND2, and KMD5A coamplification, supporting a germ cell origin. The tumors were microsatellite-stable and exhibited a low tumor mutational burden. Three tumors (30%) exhibited MYCN or MYC amplification with co-occurring inactivation of the p53 pathway via either TP53 mutations or MDM2 amplification in 2 tumors. Three additional tumors (30%) had activation of the PI3K pathway via PIK3CA and PIK3CG mutations or PIK3C2B amplification; 1 tumor with co-occurring CDK4 amplification. Gene rearrangements were detected in 3 tumors (30%), with novel BRD4::MAU2 and BCOR::CLIP2 fusions as well as an internal truncating ATRX rearrangement, respectively. In summary, ENTs arising from GCTs are molecularly heterogeneous; however, a large fraction of testicular ENTs could be stratified by 2 distinct sets of genetic alterations, including MYCN/MYC amplification with concurrent suppression of the p53 pathway, and activation of the PI3K pathway with co-occurring CDK4 amplification. Moreover, the novel gene fusions identified in a subset of testicular GCT-derived ENTs overlap with molecularly defined tumors of embryonic-type neuroectodermal features in the central nervous system, indicating the potential common driving events for tumorigenesis from different anatomical sites.

Somatic-type Malignancies of Germ Cell Origin: Molecular, Pathologic, and Clinical Features

Somatic-type malignancies (STMs) arising in germ cell tumors are relatively rare, affecting 3% to 8% of patients. These neoplasms show aggressive clinical behavior and are frequently resistant to systemic therapy. In the current review, we provide a comprehensive clinicopathologic overview of these tumors, emphasizing new molecular findings that have improved our understanding of their pathogenesis. In all areas, we highlight special considerations related to the different histologic subtypes. We conclude with a brief mention of areas of uncertainty and areas that require further study.

Mesenchymal Neoplasms of the Bladder and Male Genital Tract, including the Perineum and Scrotum

Mesenchymal neoplasms of the bladder and male genital tract are uncommonly encountered in routine diagnostic practice and present diagnostic challenges. Here, I systematically survey mesenchymal tumors at each body site, including the spermatic cord, scrotum, and perineum. I provide a detailed overview of tumor types that specifically or most commonly occur in the bladder and male genital tract, including pseudosarcomatous myofibroblastic neoplasm of the bladder, proliferative funiculitis, paratesticular sclerosing rhabdomyoma, penile myointimoma, and so-called prostatic stromal tumors.

Epithelioid trophoblastic tumor in male patients with germ cell tumor: A clinicopathologic analysis of five cases

Epithelioid trophoblastic tumor (ETT) is an extremely rare chorionic-type neoplasm in the testis, with only seven cases reported in the literature. Here, we report five cases of testicular ETT from a single institution, constituting the largest series of this rare tumor to date. The patients had a mean age of 44 years (range, 20-68 years). Four patients had a previous history of testicular germ cell tumor (GCT) treated with chemotherapy, and they developed ETT in metastatic sites in a mean of 11 years (range, 3-15 years) after the initial diagnosis of testicular GCT. Only one patient had ETT in the testis. Three patients had a normal serum beta-human chorionic gonadotropin (β-hCG) level, and two patients had a level that was slightly elevated, but far below that typically seen in patients with choriocarcinoma. ETT was characterized by a proliferation of intermediate trophoblastic cells with abundant eosinophilic cytoplasm, and the tumors frequently had coagulative necrosis with eosinophilic debris, mimicking keratinizing squamous cell carcinoma. The trophoblastic phenotype of ETT was supported by its immunoreactivity for trophoblastic markers, including GATA-3 (3 of 3 cases tested), α-inhibin (3/4), p63 (3/5), and β-hCG (3/4). ETT was also positive for cytokeratin (4/4) and GCT marker SALL4 (3/3). Despite surgery and chemotherapy, two patients died of disease 17 months after ETT diagnosis, and three patients were alive with metastatic disease at a mean of 20 months (range, 15-28 months). Our results demonstrate that ETT may be an aggressive disease associated with distinct pathologic features and poor clinical outcome.

Pathogenesis and pathobiology of testicular germ cell tumours: a view from a developmental biological perspective with guidelines for pathological diagnostics

Testicular germ cell tumours (GCT) are divided into three different subtypes (types I-III) regarding to their developmental origin, histological differences and molecular features. Type I GCT develop from disturbed primordial germ cells and most commonly occur in children and young adolescents, which is why they are referred to as prepubertal GCT. Type II GCT develop from a non-invasive germ cell neoplasia in situ (GCNIS) and show an isochromosome 12p (i12p) or gain of 12p material as a common and characteristic molecular alteration. Type III GCT originate from distorted postpubertal germ cells (e.g. spermatogonia) in adult patients and have changes on chromosome 9 with amplification of the DMRT1 gene. Type I GCT encompass prepubertal-type teratomas and yolk-sac tumours (YST). Type II GCT include seminoma, embryonal carcinoma, choriocarcinoma, postpubertal-type teratoma and postpubertal-type YST. Types I and II GCT both show similar morphology, but are separated from each other by the detection of a GCNIS and an i12p in type II GCT. For type II GCT it is especially important to detect non-seminomatous elements, as these tumours have a worse biological behaviour and need a different treatment to seminomas. In contrast to types I and II GCT, type III tumours are equivalent to spermatocytic tumours and usually occur in elderly men, with few exceptions in young adults. The development of types I and II GCT seems to depend not upon driver mutations, but rather on changes in the epigenetic landscape. Furthermore, different pluripotency associated factors (e.g. OCT3/4, SOX2, SOX17) play a crucial role in GCT development and can be used as immunohistochemical markers allowing to distinguish the different subtypes from each other in morphologically challenging tissue specimens. Especially in metastatic sites, a morphological and immunohistochemical diagnostic algorithm is important to detect small subpopulations of each non-seminomatous GCT subtype, which are associated with a poorer prognosis and need a different treatment. Furthermore, primary extragonadal GCT of the retroperitoneum or mediastinum develop from misguided germ cells during embryonic development, and might be challenging to detect in small tissue biopsies due to their rarity at corresponding sites. This review article summarises the pathobiological and developmental aspects of the three different types of testicular GCT that can be helpful in the histopathological examination of tumour specimens by pathologists.

Metastatic germ cell tumors in serous cavities and cerebrospinal fluid: A single-center experience

BACKGROUND

Metastatic germ cell tumors (GCTs) involving body cavity effusions and cerebrospinal fluid (CSF) are rare. Diagnosis is challenging because of limited morphological and clinicopathological information in the literature.

METHODS

A database search of our institution from 1990 to 2024 identified 27 cases of metastatic GCTs, comprising five pediatric and 22 adolescent and adult patients, in serous cavities or the CSF, including peritoneal (15), pleural (nine), CSF (two), and pericardial (one) fluid.

RESULTS

The most common primary site was the testis (n = 10), followed by the ovaries (n = 7), mediastinum (n = 4), retroperitoneum (n = 3), pineal gland (n = 2), and sacrum/coccyx (n = 1). The primary tumors in 14 patients were mixed GCTs (six with a seminoma component), followed by immature teratomas (six), yolk sac tumors (three), embryonal carcinomas (two), pure seminomas (one), and postpubertal teratomas (one). The median interval between primary tumor diagnosis and diagnosis of fluid positivity was 7 months (range: 0-134 months). In nine cases, the malignant fluid was diagnosed simultaneously with or within 1 month of the primary tumor. GCT subtyping was performed on 23 of the 27 cytological specimens. Twenty-four patients (89%) also had metastases to other sites. Thirteen patients died of the disease (48%), with a median survival time of 4 months.

CONCLUSIONS

Metastatic GCTs in serous effusions and CSF are often associated with disseminated disease and poor prognosis. Subtyping can be performed by cytomorphology combined with immunohistochemistry.

A comprehensive analysis of the KLRB1 expression and its clinical implication in testicular germ cell tumors: A review

Testicular germ cell tumors (TGCT) are the most common testicular malignancies. KLRB1 is considered to influence the development and progression of a number of cancers. However, it is unclear how the KLRB1 gene functions in TGCT. First, it was determined the expression level of KLRB1 in TGCT using The Cancer Genome Atlas (TCGA) (The Cancer Genome Atlas) dataset and GTEx (Genotype-Tissue Expression) dataset. The clinical significance and biological functions of KLRB1 were explored using the TCGA dataset, and we analyzed the correlation of the KLRB1 gene with tumor immunity and infiltrating immune cells using gene set variation analysis and the TIMER database. We found that the expression level of KLRB1 was upregulated in TGCT malignant tissues with the corresponding normal tissues as controls, and KLRB1 expression correlated with clinicopathologic features of TGCT. Functional enrichment analysis suggested that KLRB1 might be involved in immune response and inflammatory response. KLRB1 was highly positively correlated with natural killer cell activation in immune response and positively correlated with tumor-infiltrating immune cells. This study demonstrated for the first time the role of KLRB1 in TGCT, which may serve as a new biomarker associated with immune infiltration and provide a potential therapeutic target for the treatment of TGCT.

Mediastinal Yolk Sac Tumor With Solitary Adenocarcinoma in Subcarinal Nodal Metastases

Germ cell tumors with somatic-type solid malignancy are mostly attributed to the malignant transformation of teratomas. Herein, we describe the case of a 41-year-old man with mediastinal yolk sac tumor who presented with adenocarcinoma in nodal metastases. Computed tomography revealed enlarged subcarinal lymph nodes and an anterior mediastinal tumor, which was diagnosed as a yolk sac tumor by percutaneous biopsy. The remaining tumor was resected after chemotherapy. No viable cells were observed in the primary tumor; however, adenocarcinoma was detected in the subcarinal lymph nodes. Mediastinal yolk sac tumors can be associated with metastatic adenocarcinoma in locoregional lymph nodes.

Subgrouping testicular germ cell tumors based on immunotherapy and chemotherapy associated lncRNAs

Testicular germ cell tumors (TGCT) are the most common reproductive system malignancies in men aged 15-44 years, accounting for 95 % of all testicular tumors. Our previous studies have been shown that long non-coding RNAs (lncRNAs), such as LINC00313, TTTY14 and RFPL3S, were associated with development of TGCT. Subgrouping TGCT according to differential expressed lncRNAs and immunological characteristics is helpful to comprehensively describe the characteristics of TGCT and implement precise treatment. In this study, the TGCT transcriptome data in The Cancer Genome Atlas Program (TCGA) database was used to perform consensus clustering analysis to construct a prognostic model for TGCT. TGCT was divided into 3 subtypes C1, C2, and C3 based on the differentially expressed lncRNAs. C1 subtype was sensitive to chemotherapy drugs, while the C2 subtype was not sensitive to chemotherapy drugs, and C3 subtype may benefit from immunotherapy. We defined the C1 subtype as epidermal progression subtype, the C2 subtype as mesenchymal progression subtype, and the C3 subtype as T cell activation subtype. Subgrouping based on differentially expressed genes (DEGs) and immunological characteristics is helpful for the precise treatment of TGCT.

[Low-grade astrocytoma within a retroperitoneal teratoma: Case report]

Teratomas are neoplasms originate from germ cells and can undergo malignant transformation, the World Health Organization (WHO) classified them as teratoma with somatic-type malignancy which is uncommon and sarcomas are the histological type with the highest incidence. It is important to identify this type of tumors because influences the prognosis and survival of the patient. We present the case of a 5-month-old male, who began his condition at one month-old with constipation and increase of the abdominal circumference, imaging studies revealed an abdominal lesion, he was treated with chemotherapy and surgery. The histopathological report was immature teratoma, grade 1, with a focus of nervous tissue showing characteristics of low-grade astrocytoma.