Muhammad T. Idrees

Testicular adult granulosa cell tumors (AGCTs) are rare and show several clinical, pathological, and molecular differences with their ovarian counterparts. FOXL2 p.Cys134Trp, the ubiquitous molecular driver of ovarian AGCTs, is infrequent (~ 7%) in testicular AGCTs. Recently, FGFR1 hotspot mutations were reported as a potentially “alternative molecular driver” in FOXL2 -wild type (WT) ovarian AGCTs. A systematic assessment of FGFR1 status has not been performed in testicular AGCTs. Recently, our group analyzed a series of twenty testicular AGCTs using two NGS panels that lacked coverage of FGFR1 . Among twelve cases analyzed successfully, none harbored pathogenic FOXL2 variants. In this study, we reassessed the tumors from our prior series with an NGS panel that covers FGFR1 . Among the 14 tumors (70%) that were sequenced successfully, none harbored pathogenic FGFR1 variants. Considering the AGCTs assessed in this study and those previously reported in the literature, none of the 24 tumors analyzed to date have shown pathogenic FGFR1 variants. The present study reinforces the concept that testicular sex cord-stromal tumors classified as AGCTs are different from ovarian counterparts.

To summarise the content and significance of the recently published second edition International Collaboration on Cancer Reporting (ICCR) histopathology dataset for testicular germ cell tumours, covering the Orchiectomy specimen dataset. We highlight key updates from the first editions, including alignment with the 5th edition World Health Organization (WHO) Classification, revised staging criteria, clarified core data elements versus non‐core elements and the evidentiary basis underpinning these changes. A review of the ICCR 2nd edition dataset for Orchiectomy specimens of primary testicular tumours was performed, focusing on their development by an international expert committee using a consensus‐based approach. Core (required) and non‐core (recommended) data elements were identified along with the level of evidence supporting each, following National Health and Medical Research Council (NHMRC) criteria. Changes from the first edition were extracted by comparing dataset content and notes, informed by up‐to‐date literature through July 2024. The 2nd edition Orchiectomy dataset provides an integrated, harmonised framework for reporting testicular germ cell tumours. The dataset incorporates the WHO 5th Edition Classification of Urinary and Male Genital Tumours. Pathological staging criteria have been updated to align with the 8th edition Union for International Cancer Control (UICC)/American Joint Committee on Cancer (AJCC) tumour‐node‐metastasis (TNM) definitions. The second edition of this dataset includes changes to align the dataset with the WHO Classification of Tumours, Urinary and Male Genital Tumours, 5th edition, 2022. The ICCR dataset includes the 5th edition Corrigenda, July 2024. It was agreed that this dataset is not suitable for non‐germ cell tumours, with the hope that a new dataset, especially for sex‐cord stromal tumours, would be developed. The 2nd edition Orchiectomy dataset represents an authoritative, up‐to‐date standard for pathology reporting of primary testicular germ cell tumours. By incorporating the WHO 5th edition classifications, current TNM staging and the latest evidence on prognostic factors, this dataset facilitates uniform reporting and prognostication. The ICCR dataset underscores core data required for patient management decisions (e.g., adjuvant therapy in Stage I disease, post‐chemotherapy management) while providing flexibility through non‐core elements for additional useful information. Adoption of this internationally vetted dataset will enhance consistency, assist multidisciplinary treatment planning and align pathology reports with modern consensus guidelines and classifications. The dataset can be used in both high‐resource and limited‐resource settings without compromising the essential reporting standards.

Aims: Testicular adult granulosa cell tumours (AGCTs) are rare and show several clinical–pathological differences with their ovarian counterparts. In a limited number of prior studies, FOXL2 p.Cys134Trp, the hallmark molecular alteration of ovarian AGCT, appeared to be infrequent in testicular AGCTs. However, the number of cases analysed to date is relatively small. Methods and results: Twenty testicular AGCTs were analysed de novo using two different next‐generation sequencing ( NGS ) panels that cover sex cord‐stromal tumour ( SCST )–relevant genes, including FOXL2 , CTNNB1 , FH and DICER1 . Among 12 tumours (12/20; 60%) that were sequenced successfully, none harboured FOXL2 mutations. Eight tumours (8/12, 66.7%) showed a wild‐type ( WT ) status for all genes assessed with the panels. Three tumours harboured pathogenic or likely pathogenic CTNNB1 alterations. One of these exhibited predominant spindle cell morphology, while the other two showed focal tubular architecture. Immunohistochemistry performed in one of these tumours with available material showed β‐catenin expression in ~70% of tumor cell nuclei. The remaining AGCTs showed variants of uncertain significance (likely benign) in KIT and MED12 . Considering the tumors asseseed in this study and those previously reported in the literature, only 2 of 29 neoplasms classified as testicular AGCTs have shown a FOXL2 p. Cys134Trp mutation to date. Conclusions: The present study confirms that SCSTs classified as AGCTs differ from their ovarian counterparts in that they largely lack FOXL2 mutations.

Vasculogenic mesenchymal lesions (VMLs) are uncommon phenotypes of germ cell tumor (GCT) origin that are mostly found after chemotherapy of mediastinal yolk sac tumor (YST). These lesions typically lack expression of classical YST markers [α-fetoprotein (AFP) and glypican-3 (GPC3)]. FOXA2 and HNF1β are key inducers of the YST phenotype and co-operate to promote transcription of genes involved in YST development (AFP, GPC3, GATA3, among others). Immunohistochemical studies have shown that FOXA2 and HNF1β are more sensitive than AFP, GPC3, and GATA3 for conventional phenotypes of YST, whereas they are typically negative in sarcomatoid YST. In this study, assessment of VMLs showed that they do not express FOXA2 and HNF1β to a significant degree. These results suggest that the combined downregulation of FOXA2 and HNF1β may underlie the transformation of YST to “mesenchymal” phenotypes, with additional (still undefined) processes determining the final phenotype (sarcomatoid YST or VMLs).

Sarcomatoid yolk sac tumor postpubertal-type (YSTpt) is a rare phenotype of germ cell tumor that occurs mostly after chemotherapy. Its diagnosis is clinically relevant but challenging, due to its somewhat inconspicuous histologic features and negative/low expression of classical YSTpt makers (α-fetoprotein (AFP), glypican-3 (GPC3), and GATA3)). HNF1β is likely a key inducer of the YSTpt phenotype, acting in part by regulating the binding of FOXA2 to its target genomic sequences. Recently, immunohistochemical studies have shown that HNF1β has a sensitivity comparable to FOXA2 (higher than GPC3 and AFP) for non-sarcomatoid YSTpt. We found that sarcomatoid YSTpt did not express HNF1β (0: 8/8 (100%)), suggesting that combined downregulation of FOXA2 and HNF1β may underlie the sarcomatoid transformation in this rare phenotype of germ cell tumor.

Background: Testicular Leydig cell tumours (LCTs) are the most common type of sex cord–stromal tumour in men, representing 1%–3% of all testicular neoplasms. Among testicular sex cord–stromal tumours, CTNNB1 mutations and nuclear expression of β‐catenin have been typically associated with Sertoli cell tumour. Recent genomic analyses have shown that CTNNB1 variants are also identified in a subset of LCTs; however, the frequency and clinicopathologic associations of β‐catenin alterations remain incompletely understood in this tumour type.Methods: In this study, we evaluated 32 LCTs (five malignant/metastasizing, 27 nonmetastasizing) using β‐catenin immunohistochemistry and DNA sequencing.Results: Immunohistochemistry revealed focal or multifocal nuclear β‐catenin expression in 47% of the tumours. Diffuse nuclear β‐catenin expression (in >50% of the tumour cells) was not detected in any of the cases analysed herein. Comparison of β‐catenin‐positive and β‐catenin‐negative cases did not show significant differences in the frequency of adverse histopathologic findings or malignant clinical behaviour. DNA sequencing performed de novo on a subset of seven cases revealed the presence of exon 3 CTNNB1 variants in four of them (4/7, 57%), with variant allele frequencies (VAF) ranging from 7 to 33%. Two additional β‐catenin‐positive cases that had been sequenced as part of a previous study harboured exon 3 CTNNB1 variants at VAF of 28% and 7%, respectively.Conclusion: These results demonstrate that β‐catenin alterations are relatively common in LCT, most likely occurring as subclonal events that are not enriched in cases with aggressive features. Further studies are needed to clarify the oncogenic role of β‐catenin in this tumour type.

The current WHO classification of testicular germ cell tumors is based on the pathogenesis of the tumors driven by different genomic events. The germ cell neoplasia in situ is the precursor lesion for all malignant germ cell tumors. The current understanding of pathogenesis is that the developmental and environmental factors with the erasure of parental genomic imprinting lead to the development of abnormal gonocytes that settle in the “spermatogonial Niche” in seminiferous tubules. The abnormal primordial germ cells in the seminiferous tubules give rise to pre-GCNIS cells under the influence of TPSY and OCT4 genes. The whole genome duplication events give rise to germ cell neoplasia in situ, which further acquires alterations in 12p along with NRAS and KRAS mutations to produce seminoma. A subset of seminomas acquires KIT mutation and does not differentiate further. The remaining KIT-stable seminomas differentiate to nonseminomatous GCTs after obtaining recurrent chromosomal losses, epigenetic modification, and posttranscriptional regulation by multiple genes. Nonseminomatous germ cell tumors also develop directly from differentiated germ cell neoplasia in situ. TP53 pathway with downstream drivers may give rise to somatic-type malignancies of GCT. The GCTs are remarkably sensitive to cisplatin-based combination chemotherapy; however, resistance to cisplatin develops in up to 8% of tumors and appears to be driven by TP53/MDM2 gene mutations. Serum and Plasma miRNAs show promise in diagnosing, managing, and following up on these tumors. The mechanisms underlying the development of most tumors have been elucidated; however, additional studies are required to pinpoint the events directing specific characteristics. Advances in identifying specific molecular markers have been seen recently and may be adopted as gold standards in the future.