Genomic techniques enable diagnosis and management of children and young adults with sarcomas by identifying high-risk patients and those who may benefit from targeted therapy or participation in clinical trials. Objective: to analyze the performance of an NGS gene panel for the clinical management of pediatric sarcoma patients. We studied 53 pediatric and young adult patients diagnosed with sarcoma, from two Spanish centers. Genomic data were obtained using the Oncomine Childhood Cancer Research Assay, and categorized according to their diagnostic, predictive, or prognostic value. In 44 (83%) of the 53 patients, at least one genetic alteration was identified. In 80% of these patients, the diagnosis was obtained (n = 11) or changed (n = 9), and thus genomic data affected therapy. The most frequent initial misdiagnosis was Ewing’s sarcoma, instead of myxoid liposarcoma (FUS-DDDIT3), rhabdoid soft tissue tumor (SMARCB1), or angiomatoid fibrous histiocytoma (EWSR1-CREB1). In our series, two patients had a genetic alteration with an FDA-approved targeted therapy, and 30% had at least one potentially actionable alteration. NGS-based genomic studies are useful and feasible in diagnosis and clinical management of pediatric sarcomas. Genomic characterization of these rare and heterogeneous tumors also helps in the search for prognostic biomarkers and therapeutic opportunities.

Medulloblastoma is the primary malignant tumor of the Central Nervous System (CNS) most common in pediatrics. We present here, the histological, molecular, and functional analysis of a cohort of 88 pediatric medulloblastoma tumor samples. The WNT-activated subgroup comprised 10% of our cohort, and all WNT-activated patients had exon 3 CTNNB1 mutations and were immunostained for nuclear β-catenin. One novel heterozygous CTNNB1 mutation was found, which resulted in the deletion of β-catenin Ser37 residue (ΔS37). The ΔS37 β-catenin variant ectopically expressed in U2OS human osteosarcoma cells displayed higher protein expression levels than wild-type β-catenin, and functional analysis disclosed gain-of-function properties in terms of elevated TCF/LEF transcriptional activity in cells. Our results suggest that the stabilization and nuclear accumulation of ΔS37 β-catenin contributed to early medulloblastoma tumorigenesis.

The prevalence of hereditary cancer in children was estimated to be very low until recent studies suggested that at least 10% of pediatric cancer patients carry a germline mutation in a cancer predisposition gene. A significant proportion of pathogenic variants associated with an increased risk of hereditary cancer are variants affecting splicing. RNA splicing is an essential process involved in different cellular processes such as proliferation, survival, and differentiation, and alterations in this pathway have been implicated in many human cancers. Hereditary cancer genes are highly susceptible to splicing mutations, and among them there are several genes that may contribute to pediatric solid tumors when mutated in the germline. In this review, we have focused on the analysis of germline splicing-disrupting mutations found in pediatric solid tumors, as the discovery of pathogenic splice variants in pediatric cancer is a growing field for the development of personalized therapies. Therapies developed to correct aberrant splicing in cancer are also discussed as well as the options to improve the diagnostic yield based on the increase in the knowledge in splicing.

Background: Congenital methemoglobinemia (metHb), a rare cause of neonatal cyanosis, results from the oxidation of ferrous to ferric iron in hemoglobin (Hb). The aim of this case report is to highlight the need to broaden the differential diagnosis of neonatal cyanosis and emphasizes the role of capillary blood gas analysis and genetic testing to exclude hereditary hematological causes. We report a previously unreported genetic mutation associated with congenital metHb. Case Description: We report the case of a term male neonate with cyanosis unresponsive to oxygen administration. Complementary studies were normal, including echocardiography, cerebral ultrasound, blood tests, blood culture, cytomegalovirus testing, glucose-6-phosphate dehydrogenase (G6PD) assessment, and Hb electrophoresis, with the exception of a mild left anterior pneumothorax. There was a discrepancy between arterial oxygen pressure (PaO₂) and oxygen saturation by pulse oximetry. Ultimately, co-oximetry revealed a metHb level of 20%, confirming the diagnosis of metHb. Next generation sequencing (NGS) identified a compound heterozygous missense mutation in the cytochrome B5 reductase (CYB5R3) gene: c673C>T (p.Arg225Cys) and c977A>G (p.His326Arg), both considered pathogenic/probably pathogenic. While the first mutation is documented, the second is not previously reported as a cause of congenital metHb. This compound heterozygous genotype in the CYB5R3 gene may explain the phenotype observed in this patient with congenital metHb. Erythrocyte enzyme testing confirmed reduced CYB5R3 activity. Family genetic studies confirmed the patient’s compound heterozygosity, with one mutation inherited from each parent and genetic counseling was offered. The patient has progressed favorably, achieving appropriate psychomotor development without neurological disorders. There has been a decrease in perioral cyanosis, with metHb levels dropping to 3%. Oxygen saturation reached normal levels (96%) by 2 years of age. Conclusions: MetHb is a rare cause of cyanosis in children. The acquired form is the most common, due to exposure to oxidizing substances that increase metHb production. Congenital forms, however, are more frequent in neonates, and their evolution depends on specific mutations. Genetic testing is crucial for family counseling. Clinicians should suspect metHb in cases of cyanosis and hypoxia without respiratory distress, especially when there is no improvement with oxygen therapy and normal PaO₂, after excluding other more common causes such as respiratory, infectious and cardiological conditions.

Pediatric cancer care in Spain lacked a national personalized medicine program. The SEHOP-PENCIL initiative, established by the SEHOP, was designed to address this gap. A national survey identified the genomic sequencing needs of hospitals treating pediatric patients with cancer. Results showed improved access to targeted next-generation sequencing panels but revealed persistent variability in implementation, limited availability of advanced sequencing (whole-exome sequencing, whole-genome sequencing, RNA sequencing, and DNA methylation profiling), and gaps in cancer predisposition clinics and molecular tumor boards (MTBs). SEHOP-PENCIL is organized as a network of 10 specialized genomic centers serving 45 hospitals through a centralized inclusion system. The program standardizes patient eligibility, genomic workflows, and result interpretation, supported by a national MTB. This framework enables informed clinical decision making, ensures access to molecular diagnosis and innovative therapies, and supports systematic data collection to advance pediatric cancer research and personalized care. SEHOP-PENCIL represents a pioneering national model for integrating precision oncology into pediatric cancer care in Spain. By fostering collaboration, standardizing genomic practices, and promoting equitable access, it aims to reduce disparities and improve outcomes, offering a scalable example for other decentralized health care systems.