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Background T-cell lymphoblastic lymphoma (T-LBL) is an aggressive neoplasm closely related to T-cell acute lymphoblastic leukaemia (T-ALL). Despite their similarities, and contrary to T-ALL, studies on paediatric T-LBL are scarce and, therefore, its molecular landscape has not yet been fully elucidated. Thus, the aims of this study were to characterize the genetic and molecular heterogeneity of paediatric T-LBL and to evaluate novel molecular markers differentiating this entity from T-ALL. Procedure Thirty-three paediatric T-LBL patients were analyzed using an integrated approach, including targeted next-generation sequencing, RNA-sequencing transcriptome analysis and copy-number arrays. Results Copy number and mutational analyses allowed the detection of recurrent homozygous deletions of 9p/CDKN2A (78%), trisomy 20 (19%) and gains of 17q24-q25 (16%), as well as frequent mutations of NOTCH1 (62%), followed by the BCL11B (23%), WT1 (19%) and FBXW7, PHF6 and RPL10 genes (15%, respectively). This genetic profile did not differ from that described in T-ALL in terms of mutation incidence and global genomic complexity level, but unveiled virtually exclusive 17q25 gains and trisomy 20 in T-LBL. Additionally, we identified novel gene fusions in paediatric T-LBL, including NOTCH1-IKZF2, RNGTT-SNAP91 and DDX3X-MLLT10, the last being the only one previously described in T-ALL. Moreover, clinical correlations highlighted the presence of Notch pathway alterations as a factor related to favourable outcome. Conclusions In summary, the genomic landscape of paediatric T-LBL is similar to that observed in T-ALL, and Notch signaling pathway deregulation remains the cornerstone in its pathogenesis, including not only mutations but fusion genes targeting NOTCH1. We thank the centres of the Sociedad Espanola de Hematologia y Oncologia Pediatricas that submitted cases for consultation, to Noelia Garcia, Silvia Martin and Helena Suarez for their excellent technical assistance and to Nerea Dominguez for updating clinical data. We are indebted to the IDIBAPS Genomics Core Facility and to the HCB-IDIBAPS, the HospitaI Infantil Sant Joan de Deu and the Hospital Universitari Vall d'Hebron Tumour Biobanks, all integrated in the National Network Biobanks of ISCIII for the sample and data procurement. This work was supported by Asociacion Espanola Contra el Cancer (AECC CICPFI6025SALA and 'Ayudas Clinico Formacion AECC 2020' to Jaime Verdu-Amoros), Asociacion de aitas y amas para la humanizacion, socializacion e investigacion del Cancer Infantil y la divulgacion de la donacion de medula osea-La Cuadri del Hospi, Fondo de Investigaciones Sanitarias Instituto de Salud Carlos III (Miguel Servet Program I and II CP13/00159 and MSII18/00015; Itziar Salaverria), Generalitat de Catalunya Suport Grups de Recerca (2017-SGR-1107; Itziar Salaverria), and the European Regional Development Fund 'Una manera de fer Europa'. Joan Enric Ramis-Zaldivar was supported by a fellowship AGAUR FI-DGR 2017 (2017 FI_B01004) from Generalitat de Catalunya. Noelia Garcia has been continuously supported by Accio instrumental d'incorporacio de cientifics i tecnlegs PERIS 2016 (SLT002/16/00336) and PERIS 2020 (SL017/20/000204) from Generalitat de Catalunya. Julia Salmeron-Villalobos was supported by a fellowship from La Caixa (CLLEvolution-HR17-00221). This work was developed partially at the Centro Esther Koplowitz, Barcelona, Spain.

Childhood acute lymphoblastic leukemia (ALL), the most common pediatric cancer, is a heterogeneous disease comprised of multiple molecular subtypes with distinct somatic genetic alterations, which results in different outcomes for the patients. Accurate patient risk stratification through genetic markers could increase survival rates, but the identification of reliable biomarkers is needed, as 20‑30% of B‑ALL patients cannot be classified in the clinic with routine techniques and some patients classified as low‑risk and good‑responders to treatment will eventually relapse. Long non‑coding RNAs (lncRNAs) can represent novel candidates with diagnostic, classification, prognosis, and treatment response potential. However, regarding childhood ALL, there is inconsistency in the data reported due to the lack of a consensus nomenclature for lncRNA naming and the methodology and designing applied for their study. Therefore, the aim of the article is to clarify the potential of lncRNAs as biomarkers in childhood ALL through a systematic review. From a revision of 23 manuscripts, it was found that