RAF1 gene fusions are recurrent driver events in infantile fibrosarcoma-like mesenchymal tumors.

Infantile fibrosarcomas (IFS) and congenital mesoblastic nephroma (CMN) are rare myofibroblastic tumors of infancy and early childhood commonly harboring the ETV6::NTRK3 gene fusion. IFS/CMN are considered as tumors with an 'intermediate prognosis' as they are locally aggressive, but rarely metastasize, and generally have a favorable outcome. A fraction of IFS/CMN-related neoplasms are negative for the ETV6::NTRK3 gene rearrangement and are characterized by other chimeric proteins promoting MAPK signaling upregulation. In a large proportion of these tumors, which are classified as IFS-like mesenchymal neoplasms, the contributing molecular events remain to be identified. Here, we report three distinct rearrangements involving RAF1 among eight ETV6::NTRK3 gene fusion-negative tumors with an original histological diagnosis of IFS/CMN. The three fusion proteins retain the entire catalytic domain of the kinase. Two chimeric products, GOLGA4::RAF1 and LRRFIP2::RAF1, had previously been reported as driver events in different cancers, whereas the third, CLIP1::RAF1, represents a novel fusion protein. We demonstrate that CLIP1::RAF1 acts as a bona fide oncoprotein promoting cell proliferation and migration through constitutive upregulation of MAPK signaling. We show that the CLIP1::RAF1 hyperactive behavior does not require RAS activation and is mediated by constitutive 14-3-3 protein-independent dimerization of the chimeric protein. As previously reported for the ETV6::NTRK3 fusion protein, CLIP1::RAF1 similarly upregulates PI3K-AKT signaling. Our findings document that RAF1 gene rearrangements represent a recurrent event in ETV6::NTRK3-negative IFS/CMN and provide a rationale for the use of inhibitors directed to suppress MAPK and PI3K-AKT signaling in these cancers. © 2024 The Pathological Society of Great Britain and Ireland.

Clinicopathological and molecular landscape of 5-year IDH-wild-type glioblastoma survivors: A multicentric retrospective study.

Five-year glioblastoma (GBM) survivors (LTS) are the minority of the isocitrate dehydrogenase (IDH)-wild-type GBM patients, and their molecular fingerprint is still largely unexplored. This multicenter retrospective study analyzed a large LTS-GBM cohort from nine Italian institutions and molecularly characterized a subgroup of patients by mutation, DNA methylation (DNAm) and copy number variation (CNV) profiling, comparing it to standard survival GBM. Mutation scan allowed the identification of pathogenic variants in most cases, showing a similar mutational spectrum in both groups, and highlighted TP53 as the most commonly mutated gene in the LTS group. We confirmed DNAm as a valuable tool for GBM classification with a diagnostic refinement by using brain tumor classifier v12.5. LTS were more heterogeneous with more cases classified as diffuse pediatric high-grade glioma subtypes and having peculiar CNVs. We observed a global higher methylation in CpG islands and in gene promoters of LTS with methylation levels of distinct gene promoters correlating with prognosis.

Malignant peripheral nerve sheath tumor (MPNST) and MPNST-like entities are defined by a specific DNA methylation profile in pediatric and juvenile population.

BACKGROUND: Malignant peripheral nerve sheath tumors (MPNSTs) account for 3-10% of pediatric sarcomas, 50% of which occur in neurofibromatosis type 1 (NF1). Sporadic MPNSTs diagnosis may be challenging due to the absence of specific markers, apart from immunohistochemical H3K27me3 loss. DNA methylation (DNAm) profiling is a useful tool for brain and mesenchymal neoplasms categorization, and MPNSTs exhibit a specific DNAm signature. An MPNST-like group has recently been recognized, including pediatric tumors with retained H3K27me3 mark and clinical/histological features not yet well explored. This study aims to characterize the DNAm profile of pediatric/juvenile MPNSTs/MPNST-like entities and its diagnostic/prognostic relevance. RESULTS: We studied 42 tumors from two groups. Group 1 included 32 tumors histologically diagnosed as atypical neurofibroma (ANF) (N = 5) or MPNST (N = 27); group 2 comprised 10 tumors classified as MPNST-like according to Heidelberg sarcoma classifier. We performed further immunohistochemical and molecular tests to reach an integrated diagnosis. In group 1, DNAm profiling was inconclusive for ANF; while, it confirmed the original diagnosis in 12/27 MPNSTs, all occurring in NF1 patients. Five/27 MPNSTs were classified as MPNST-like: Integrated diagnosis confirmed MPNST identity for 3 cases; while, the immunophenotype supported the change to high-grade undifferentiated spindle cell sarcoma in 2 samples. The remaining 10/27 MPNSTs variably classified as schwannoma, osteosarcoma, BCOR-altered sarcoma, rhabdomyosarcoma (RMS)-MYOD1 mutant, RMS-like, and embryonal RMS or did not match with any defined entity. Molecular analysis and histologic review confirmed the diagnoses of BCOR, RMS-MYOD1 mutant, DICER1-syndrome and ERMS. Group 2 samples included 5 high-grade undifferentiated sarcomas/MPNSTs and 5 low-grade mesenchymal neoplasms. Two high-grade and 4 low-grade lesions harbored tyrosine kinase (TRK) gene fusions. By HDBSCAN clustering analysis of the whole cohort we identified two clusters mainly distinguished by H3K27me3 epigenetic signature. Exploring the copy number variation, high-grade tumors showed frequent chromosomal aberrations and CDKN2A/B loss significantly impacted on survival in the MPNSTs cohort. CONCLUSION: DNAm profiling is a useful tool in diagnostic work-up of MPNSTs. Its application in a retrospective series collected during pre-molecular era contributed to classify morphologic mimics. The methylation group MPNST-like is a 'hybrid' category in pediatrics including high-grade and low-grade tumors mainly characterized by TRK alterations.

CNS tumor with CREBBP::BCORL1 Fusion and pathogenic mutations in BCOR and CREBBP: expanding the spectrum of BCOR-altered tumors.

The fifth edition of the World Health Organization (WHO) classification of central nervous system (CNS) tumors introduced the new tumor type CNS tumor with BCOR internal tandem duplication (ITD), characterized by a distinct DNA methylation profile and peculiar histopathological features, including a circumscribed growth pattern, ependymoma-like perivascular pseudorosettes, microcystic pattern, absent or focal GFAP immunostaining, OLIG2 positivity, and BCOR immunoreactivity. We describe a rare case of a CNS tumor in a 45-year-old man with histopathological and immunohistochemical features overlapping the CNS tumor with BCOR internal tandem duplication (ITD) but lacking BCOR immunostaining and BCOR ITD. Instead, the tumor showed CREBBP::BCORL1 fusion and pathogenic mutations in BCOR and CREBBP, along with a DNA methylation profile matching the "CNS tumor with EP300:BCOR(L1) fusion" methylation class. Two CNS tumors with fusions between CREBBP, or its paralog EP300, and BCORL1, and approximately twenty CNS tumors with CREBBP/EP300::BCOR fusions have been reported to date. They exhibited similar ependymoma-like features or a microcystic pattern, along with focal or absent GFAP immunostaining, and shared the same DNA methylation profile. Given their morphological and epigenetic similarities, circumscribed CNS tumors with EP300/CREBBP::BCOR(L1) fusions and CNS tumors with BCOR ITD may represent variants of the same tumor type. The ependymoma-like aspect coupled with the lack of diffuse GFAP immunostaining and the presence of OLIG2 positivity are useful clues for recognizing these tumors in histopathological practice. The diagnosis should be confirmed after testing for BCOR(L1) gene fusions and BCOR ITD.

PATZ1-Rearranged Tumors of the Central Nervous System: Characterization of a Pediatric Series of Seven Cases.

PATZ1-rearranged sarcomas are well-recognized tumors as part of the family of round cell sarcoma with EWSR1-non-ETS fusions. Whether PATZ1-rearranged central nervous system (CNS) tumors are a distinct tumor type is debatable. We thoroughly characterized a pediatric series of PATZ1-rearranged CNS tumors by chromosome microarray analysis (CMA), DNA methylation analysis, gene expression profiling and, when frozen tissue is available, optical genome mapping (OGM). The series consisted of 7 cases (M:F=1.3:1, 1-17 years, median 12). On MRI, the tumors were supratentorial in close relation to the lateral ventricles (intraventricular or iuxtaventricular), preferentially located in the occipital lobe. Two major histologic groups were identified: one (4 cases) with an overall glial appearance, indicated as "neuroepithelial" (NET) by analogy with the corresponding methylation class (MC); the other (3 cases) with a predominant spindle cell sarcoma morphology, indicated as "sarcomatous" (SM). A single distinct methylation cluster encompassing both groups was identified by multidimensional scaling analysis. Despite the epigenetic homogeneity, unsupervised clustering analysis of gene expression profiles revealed 2 distinct transcriptional subgroups correlating with the histologic phenotypes. Interestingly, genes implicated in epithelial-mesenchymal transition and extracellular matrix composition were enriched in the subgroup associated to the SM phenotype. The combined use of CMA and OGM enabled the identification of chromosome 22 chromothripsis in all cases suitable for the analyses, explaining the physical association of PATZ1 to EWSR1 or MN1. Six patients are currently disease-free (median follow-up 30 months, range 12-92). One patient of the SM group developed spinal metastases at 26 months from diagnosis and is currently receiving multimodal therapy (42 months). Our data suggest that PATZ1-CNS tumors are defined by chromosome 22 chromothripsis as causative of PATZ1 fusion, show peculiar MRI features (eg, relation to lateral ventricles, supratentorial frequently posterior site), and, although epigenetically homogenous, encompass 2 distinct histologic and transcriptional subgroups.

Bi-allelic genetic variants in the translational GTPases GTPBP1 and GTPBP2 cause a distinct identical neurodevelopmental syndrome.

The homologous genes GTPBP1 and GTPBP2 encode GTP-binding proteins 1 and 2, which are involved in ribosomal homeostasis. Pathogenic variants in GTPBP2 were recently shown to be an ultra-rare cause of neurodegenerative or neurodevelopmental disorders (NDDs). Until now, no human phenotype has been linked to GTPBP1. Here, we describe individuals carrying bi-allelic GTPBP1 variants that display an identical phenotype with GTPBP2 and characterize the overall spectrum of GTP-binding protein (1/2)-related disorders. In this study, 20 individuals from 16 families with distinct NDDs and syndromic facial features were investigated by whole-exome (WES) or whole-genome (WGS) sequencing. To assess the functional impact of the identified genetic variants, semi-quantitative PCR, western blot, and ribosome profiling assays were performed in fibroblasts from affected individuals. We also investigated the effect of reducing expression of CG2017, an ortholog of human GTPBP1/2, in the fruit fly Drosophila melanogaster. Individuals with bi-allelic GTPBP1 or GTPBP2 variants presented with microcephaly, profound neurodevelopmental impairment, pathognomonic craniofacial features, and ectodermal defects. Abnormal vision and/or hearing, progressive spasticity, choreoathetoid movements, refractory epilepsy, and brain atrophy were part of the core phenotype of this syndrome. Cell line studies identified a loss-of-function (LoF) impact of the disease-associated variants but no significant abnormalities on ribosome profiling. Reduced expression of CG2017 isoforms was associated with locomotor impairment in Drosophila. In conclusion, bi-allelic GTPBP1 and GTPBP2 LoF variants cause an identical, distinct neurodevelopmental syndrome. Mutant CG2017 knockout flies display motor impairment, highlighting the conserved role for GTP-binding proteins in CNS development across species.

Intrathoracic synovial sarcoma with BRAF V600E mutation.

We report a case of 15-year-old boy with intrathoracic synovial sarcoma who relapsed after standard chemotherapy, surgery and radiotherapy. The molecular analysis of the tumour identified a BRAF V600E mutation at time of progression of relapsed disease under third line systemic treatment. This mutation is commonly seen in melanomas and papillary thyroid cancers, but less prevalent (typically <5%) across a variety of other cancer types. The patient underwent selective BRAF inhibitor Vemurafenib treatment achieving partial response (PR) with a progression free survival (PFS) ratio of 1.6 months and an overall survival of 19 months, alive in continuous PR. This case highlights the role of routinely next generation sequencing (NGS) used to drive treatment choice and to investigate extensively synovial sarcoma tumour for BRAF mutation.

Intracranial mesenchymal tumor with (novel) COX14::PTEN rearrangement.

Mesenchymal tumors of the central nervous system (CNS) include numerous entities, with different pathological features and biological behavior. Mesenchymal non-meningothelial tumors are rare and comprise neoplasms that are exclusive to the CNS or show peculiar features when occurring in the CNS compared with other sites. Within this group there are three new entities, classified on the basis of specific molecular alterations and included in the 5th edition of the WHO Classification of CNS Tumors: primary intracranial sarcoma; DICER1-mutant; CIC-rearranged sarcoma; intracranial mesenchymal tumor, FET::CREB fusion-positive. These tumors often show variable morphology, making diagnosis very challenging, although the implementation of molecular techniques has led to better characterization and more precise identification of these entities. However, many molecular alterations have yet to be discovered and some recently reported CNS tumors are currently missing an appropriate classification. Herein, we report the case of a 43-year-old man who presented with an intracranial mesenchymal tumor. Histopathological examination showed a wide spectrum of peculiar morphological features and a non-specific immunohistochemical profile. Whole transcriptome sequencing revealed the presence of a novel genetic rearrangement involving COX14 and PTEN genes, which has never been reported before in any other neoplasm. The tumor did not cluster in any defined methylation class of the brain tumor classifier, but resulted in a calibrated score of 0.89 for the methylation class "Sarcoma, MPNST-like", when analyzed by the sarcoma classifier. Our study is the first to report about this tumor with unique pathological and molecular features, characterized by a novel rearrangement between COX14 and PTEN genes. Other studies are necessary in order to define it as a new entity or as a novel rearrangement involving recently described and incompletely characterized CNS mesenchymal tumors.

Defective peripheral B cell selection in common variable immune deficiency patients with autoimmune manifestations.

Common variable immune deficiency (CVID) is a heterogeneous disorder characterized by recurrent infections, low levels of serum immunoglobulins, and impaired vaccine responses. Autoimmune manifestations are common, but B cell central and peripheral selection mechanisms in CVID are incompletely understood. Here, we find that receptor editing, a measure of central tolerance, is increased in transitional B cells from CVID patients and that these cells have a higher immunoglobulin κ:λ ratio in CVID patients with autoimmune manifestations than in those with infection only. Contrariwise, the selection pressure in the germinal center on CD27bright memory B cells is decreased in CVID patients with autoimmune manifestations. Finally, functionally, T cell-dependent activation showed that naive B cells in CVID patients are badly equipped for activation and induction of mismatch repair genes. We conclude that central tolerance is functional whereas peripheral selection is defective in CVID patients with autoimmune manifestations, which could underpin the development of autoimmunity.

Case report: Novel compound heterozygosity for pathogenic variants in MED23 in a syndromic patient with postnatal microcephaly.

Biallelic loss-of-function variants in MED23 cause a recessive syndromic intellectual disability condition with or without epilepsy (MRT18). Due to the small number of reported individuals, the clinical phenotype of the disorder has not been fully delineated yet, and the spectrum and frequency of neurologic features have not been fully characterized. Here, we report a 5-year-old girl with compound heterozygous for two additional MED23 variants. Besides global developmental delay, axial hypotonia and peripheral increased muscular tone, absent speech, and generalized tonic seizures, which fit well MRT18, the occurrence of postnatal progressive microcephaly has been here documented. A retrospective assessment of the previously reported clinical data for these subjects confirms the occurrence of postnatal progressive microcephaly as a previously unappreciated feature of the phenotype of MED23-related disorder.

Paediatric-type diffuse high-grade gliomas in the 5th CNS WHO Classification.

As a relevant element of novelty, the fifth CNS WHO Classification highlights the distinctive pathobiology underlying gliomas arising primarily in children by recognizing for the first time the families of paediatric-type diffuse gliomas, both high-grade and low-grade. This review will focus on the family of paediatric-type diffuse high-grade gliomas, which includes four tumour types: 1) Diffuse midline glioma H3 K27-altered; 2) Diffuse hemispheric glioma H3 G34-mutant; 3) Diffuse paediatric-type high-grade glioma H3-wildtype and IDH-wildtype; and 4) Infant-type hemispheric glioma. The essential and desirable diagnostic criteria as well as the entities entering in the differential will be discussed for each tumour type. A special focus will be given on the issues encountered in the daily practice, especially regarding the diagnosis of the diffuse paediatric-type high-grade glioma H3-wildtype and IDH-wildtype. The advantages and the limits of the multiple molecular tests which may be utilised to define the entities of this tumour family will be evaluated in each diagnostic context.

CAPRIN1P512L causes aberrant protein aggregation and associates with early-onset ataxia.

CAPRIN1 is a ubiquitously expressed protein, abundant in the brain, where it regulates the transport and translation of mRNAs of genes involved in synaptic plasticity. Here we describe two unrelated children, who developed early-onset ataxia, dysarthria, cognitive decline and muscle weakness. Trio exome sequencing unraveled the identical de novo c.1535C > T (p.Pro512Leu) missense variant in CAPRIN1, affecting a highly conserved residue. In silico analyses predict an increased aggregation propensity of the mutated protein. Indeed, overexpressed CAPRIN1P512L forms insoluble ubiquitinated aggregates, sequestrating proteins associated with neurodegenerative disorders (ATXN2, GEMIN5, SNRNP200 and SNCA). Moreover, the CAPRIN1P512L mutation in isogenic iPSC-derived cortical neurons causes reduced neuronal activity and altered stress granule dynamics. Furthermore, nano-differential scanning fluorimetry reveals that CAPRIN1P512L aggregation is strongly enhanced by RNA in vitro. These findings associate the gain-of-function Pro512Leu mutation to early-onset ataxia and neurodegeneration, unveiling a critical residue of CAPRIN1 and a key role of RNA-protein interactions.

Angioimmunoblastic T-Cell Lymphoma with Exuberant CD30-Positive Follicular Dendritic Cell Proliferation in a SARS-CoV-2 Patient: The Role of Mutational Analysis to Exclude an Associated Follicular Dendritic Cell Sarcoma.

Follicular dendritic cell (FDC) proliferation in angioimmunoblastic T-cell lymphoma (AITL) is still not well defined, challenging the accurate differential diagnosis between the AITL with expanded follicular dendritic cell meshwork and the combined AITL and follicular dendritic cell sarcoma (FDCS). Herein, we reported the case of a 58-year-old male with coexisting SARS-CoV-2 infection and AITL with an exuberant CD30-positive FDC proliferation, in which genetic analysis identified mutations of genes commonly involved in AITL but not in FDC sarcoma (i.e., RHOA, TET2, DNMT3A, and IDH2), thus supporting the reactive nature of the CD30-positive FDC expansion.

Rethinking the Management of Optic Pathway Gliomas: A Single Center Experience.

Background: Optic pathway gliomas (OPGs) are rare neoplasms in children with an unpredictable clinical course. Approximately 15% of OPGs occur in patients affected by neurofibromatosis type 1 (NF1): the clinical course of these cases is more indolently than sporadic ones, and NF1 patients less frequently require treatment including surgery. Instead, over 90% of sporadic OPGs require one or more therapeutic approaches. The management of OPG is controversial. They are also characterized by a high risk of morbidity including hypothalamic damage, endocrine deficits, visual deficit and/or neurological impairment. Materials and Methods: In this paper, we evaluated visual and endocrinological outcomes of a population of OPG followed at our center from 2013 to 2021, with a particular emphasis on the role of surgery. Results: Twenty-six patients were included in this study (mean age of 40.7 months). Tumor location on imaging was described by the Dodge classification. Five cases had NF 1. Thirteen cases received biopsy and 13 were partially resected. Histopathology revealed 19 cases of pilocytic astrocytomas, 2 pilomyxoid astrocytoma and 5 ganglioglioma. All the patients required a post-surgical adjuvant treatment according to current indications for low-grade gliomas. Molecular studies (BRAF status and mTOR/pmTOR pathway) have been performed in 24/26 patients, following for the use of target therapy in 11 of these patients. In our study we found that patients underwent biopsy have a better visual and endocrinological outcomes rather than patients with a tumor debulking. The five-year overall survival rate is 98% with a mean follow-up of 60 months. Conclusions: Many children with OPGs survive with a residual tumor. They suffer from chronic diseases such as endocrine dysfunction, visual disturbance, motor deficits and poor quality of life. All patients need comprehensive diagnostic work-up including neuroimaging, clinical evaluations and neuropathology approach; at the same time, they need therapeutic decisions and concepts for the choice of timing and type of neurosurgical intervention, chemotherapy and target therapy as well as surveillance and rehabilitation to maximize survival and overall functional outcomes. Our study showed that minimal invasive surgery with the purpose of molecular characterization of the tumor is desirable to reduce morbidity correlate to surgery.

Paediatric astroblastoma-like neuroepithelial tumour of the spinal cord with a MAMLD1-BEND2 rearrangement.

Astroblastomas are neuroepithelial tumours defined by the presence of MN1 rearrangement and are typically located in the cerebral hemispheres. Rare cases of astroblastoma-like tumours carrying an EWSR1-BEND2 fusion have been recently described in the brain stem and spinal cord. We report a paediatric case of neuroepithelial astroblastoma-like tumour occurring in the spine and carrying a novel MAMLD1-BEND2 fusion. We believe that our case aligns with the rare astroblastoma-like tumours with EWSR1-BEND2 fusion, in terms of non-hemispheric location, pathology, methylation profile and activation of BEND2 transcription. Whether they may represent a distinct entity or a variant of MN1-altered astroblastoma is not clear.

Cerebellar Agenesis and Bilateral Polimicrogyria Associated with Rare Variants of CUB and Sushi Multiple Domains 1 Gene (CSMD1): A Longitudinal Neuropsychological and Neuroradiological Case Study.

Cerebellar agenesis is an extremely rare condition characterized by a near complete absence of the cerebellum. The pathogenesis and molecular basis remain mostly unknown. We report the neuroradiological, molecular, neuropsychological and behavioral characterization of a 5-year-old girl, with cerebellar agenesis associated with parietal and peri-Sylvian polymicrogyria, followed-up for 10 years at four time points. Whole exome sequencing identified two rare variants in CSMD1, a gene associated with neurocognitive and psychiatric alterations. Mild intellectual impairment, cerebellar ataxia and deficits in language, memory and executive functions, with relatively preserved adaptive and psychopathological domains, were initially showed. Phonological awareness and verbal memory declined at 11 years of age, and social and anxiety problems emerged. Adaptive and psychopathological characteristics dramatically worsened at 15 years. In summary, the developmental clinical outcome showed impairment in multiple cognitive functions in childhood, with a progressive decline in cognitive and adaptive abilities and the emergence of psychopathological symptoms in adolescence. The observed phenotype could be the result of a complex interplay between cerebellar abnormality, brain malformation and the relations with CSMD1 variants. These findings may provide insights into the developmental clinical outcomes of a co-occurrence between rare brain malformation and rare genetic variants associated to neurodevelopmental disorders.

Molecular Landscape in Infant High-Grade Gliomas: A Single Center Experience.

High-grade gliomas (HGG) represent about 15% of all pediatric brain tumors, with a dismal prognosis and survival rates ranging from 15 to 35%. Approximately 10-12% of pediatric HGGs (pHGG) occur in children younger than five years of age at diagnosis, specifically infants (iHGG), with an unexpected overall survival rate (OS) in 60-70% of cases. In the literature, iHGGs include a large variety of heterogeneous lesions with different molecular profiles that likely explain their different outcomes. We report our single-institution experience of iHGG including 11 children under five years of age with newly diagnosed HGG between 2011 and 2021. All patients received surgery and adjuvant chemotherapy; only two patients received radiotherapy because their age at diagnosis was more than four years-old. Molecular investigations, including next generation sequencing (NGS) and DNA methylation, detected three NTRK-fusions, one ROS1-fusions, one MN1-rearrangement, and two PATZ1-fusions. According to the molecular results, when chemotherapy failed to control the disease, two patients benefited from target therapy with a NTRK-Inhibitor larotrectinib, achieving a complete remission and a very good partial response, respectively, and no severe side-effects. In conclusion, molecular investigations play a fundamental role in the diagnostic work-up and also in the therapeutic decision. Their routine use in clinical practice could help to replace highly toxic chemotherapy regimens with a target therapy that has moderate adverse effects, even in long-term follow-up.

Adducted Thumb and Peripheral Polyneuropathy: Diagnostic Supports in Suspecting White-Sutton Syndrome: Case Report and Review of the Literature.

One of the recently described syndromes emerging from the massive study of cohorts of undiagnosed patients with autism spectrum disorders (ASD) and syndromic intellectual disability (ID) is White-Sutton syndrome (WHSUS) (MIM #616364), caused by variants in the POGZ gene (MIM *614787), located on the long arm of chromosome 1 (1q21.3). So far, more than 50 individuals have been reported worldwide, although phenotypic features and natural history have not been exhaustively characterized yet. The phenotypic spectrum of the WHSUS is broad and includes moderate to severe ID, microcephaly, variable cerebral malformations, short stature, brachydactyly, visual abnormalities, sensorineural hearing loss, hypotonia, sleep difficulties, autistic features, self-injurious behaviour, feeding difficulties, gastroesophageal reflux, and other less frequent features. Here, we report the case of a girl with microcephaly, brain malformations, developmental delay (DD), peripheral polyneuropathy, and adducted thumb-a remarkable clinical feature in the first years of life-and heterozygous for a previously unreported, de novo splicing variant in POGZ. This report contributes to strengthen and expand the knowledge of the clinical spectrum of WHSUS, pointing out the importance of less frequent clinical signs as diagnostic handles in suspecting this condition.

DICER1-associated malignancies mimicking germ cell neoplasms: Report of two cases and review of the literature.

DICER1 syndrome is characterized by a unique combination of features and a growing list of associated rare tumors. Traditionally, gonadal or extra-gonadal teratomas have not been considered part of this spectrum, with only rare DICER1-related teratoid neoplasms recently reported. Besides, their methylation profiles remain elusive. We report two DICER1-associated malignancies involving the lumbar spine of a 22-year-old man (case 1) and the pelvic cavity of a 14-year-old girl (case 2). Both tumors exhibited teratoma-like features with a high-grade malignant somatic component, including rhabdomyosarcomatous elements for case 1 and a malignant neuroectodermal neoplasm with features of an embryonal tumor with multilayered rosettes (ETMR) for case 2. Both tumors showed strong SALL4 expression and H3K27me3 loss by immunohistochemistry. Next-generation sequencing studies confirmed biallelic DICER1 mutations with additional pathogenic missense mutations in KRAS (case 1) and CTNNB1 (case 2). The methylation profile of case 1 clustered with DICER1-associated sarcomas, whereas case 2 classified as an ETMR (albeit low raw and calibrated score). In conclusion, we report two DICER1-related malignancies with teratoma-like features, further expanding their morphologic spectrum and highlighting the multipotentiality of their presumed cell of origin. Notably, we describe the first ETMR identified outside the CNS with a documented DICER1 biallelic inactivation. Our findings also highlight the potential role of other molecular alterations such as KRAS and CTNNB1 mutations in defining the phenotype of embryonal and primitive DICER1-associated neoplasms, a notion that deserves further studies.