Constitutional mismatch repair-deficiency (CMMRD) syndrome, alternatively known as biallelic mismatch repair deficiency syndrome, occurs in subset of pediatric cancer patients, including those with primary brain tumors.Patients from Arab and other developing countries are predicted to have higher incidence of CMMRD due to high prevalence of consanguinity.Integration of molecular and/or genomic testing into routine clinical care for pediatric cancer patients is important to identify patients with CMMRD syndrome.Patient with CMMRD-associated cancers may show increased responsiveness to immune checkpoint inhibitors.To the authors' knowledge, this is the first report in the Arab world of a durable response to immune checkpoint inhibitors in a pediatric glioblastoma patient.

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Brain tumors are the leading cause of childhood cancer-related deaths. Similar to adult brain tumors, pediatric brain tumors are classified based on histopathological evaluations. However, pediatric brain tumors are often histologically inconsistent with adult brain tumors. Recent research findings from molecular genetic analyses have revealed molecular and genetic changes in pediatric tumors that are necessary for appropriate classification to avoid misdiagnosis, the development of treatment modalities, and the clinical management of tumors. As many of the molecular-based therapies developed from clinical trials on adults are not always effective against pediatric brain tumors, recent advances have improved our understanding of the molecular profiles of pediatric brain tumors and have led to novel epigenetic and immunotherapeutic treatment approaches currently being evaluated in clinical trials. In this review, we focus on primary malignant brain tumors in children and genetic, epigenetic, and molecular characteristics that differentiate them from brain tumors in adults. The comparison of pediatric and adult brain tumors highlights the need for treatments designed specifically for pediatric brain tumors. We also discuss the advancements in novel molecularly targeted drugs and how they are being integrated with standard therapy to improve the classification and outcomes of pediatric brain tumors in the future.

Background: Non-Hodgkin's lymphoma is an aggressive malignant disease in children and adolescents. Although it is the fourth most common malignancy in Saudi children as reported in Saudi cancer registry, less information is available about pediatric Non-Hodgkin lymphoma and its outcome in Saudi Arabia. Study Objectives: To provide demographic data, disease characteristics, treatment protocol, toxicity and outcome of treatment in children & adolescents with Non-Hodgkin's lymphoma treated at KFMC. This study will form base line for future studies about pediatric Non-Hodgkin's lymphoma in KFMC, which may help to improve outcome for children with cancer in Saudi Arabia. Study Patients and Method: We retrospectively analyzed 28 children and adolescents diagnosed to have Non-Hodgkin's lymphoma at KFMC between December 2006 and December 2013, followed-up through June 2014. Results: Of the 28 patients, 10 (35.7%) girls and 18 (64.3%) boys, the male-to-female ratio was 1.8; 1. The median age at time of diagnosis was 6.4 years old (range 2.0 to 13.0 years old). The majority of patients (64.3%) were aged between 5 and 12 years old. Burkitt's lymphoma BL/BLL was the most common pathological subtype (60.7%), and DLBCL was the second most common subtype (21.4%). Abdominal and Retroperitoneal involvement was the most common primary site (78.6%) including the ileocaecal region. Most of the children presented with advanced Stage III and IV (75%), Cytogenetic study which screens specif-* Corresponding author. N. A. Mobark et al. 300 ically for the t (8; 14) (q24; q32) a characteristic genetic feature of Burkitt's Lymphoma was obtained from 21 patients, variant rearrangement was observed in 3/21 samples and complex chromosomes karyotype in addition to IGH/MYC rearrangement was observed in 2/21 samples. Those patients presented with very aggressive lymphoma and combined BM and CNS involvement. We use the French-American-British Mature B-Cell Lymphoma 96 Protocol (FAB LMB 96) for treatment fornewly diagnosed Mature B-Cell type NHL and high risk ALL CCG 1961 Protocol for lymphoblastic lymphoma and international Anaplastic Large Cell Lymphoma 99 Study Protocol for ALCL. The median follow-up in patients not experiencing an adverse event was 53.1 months. The estimated 3-year EFE and OS rates in the entire cohort of patients with newly diagnosed NHL treated in the KFMC were 85.2% and 89.2% respectively; Overall survival (OS) rate of patients with mature B-cell-NHL was 88.9%. Conclusion: The outcomes and survival in our small series appeared to be excellent compared with those reported in other international trials even though most of our patients presented in advanced stage of the disease. We feel that the importance of the current study is to document the relative distribution of various types of pediatric non-Hodgkin's lymphomas and age-specific distribution in different Histological subtypes.

Pediatric Low Grade Gliomas (PLGGs) display heterogeneity regarding morphology, genomic drivers and clinical outcomes. The treatment modality dictates the outcome and optimizing patient management can be challenging. In this study, we profiled a targeted panel of cancer-related genes in 37 Saudi Arabian patients with pLGGs to identify genetic abnormalities that can inform prognostic and therapeutic decision-making. We detected genetic alterations (GAs) in 97% (36/37) of cases, averaging 2.51 single nucleotide variations (SNVs) and 0.91 gene fusions per patient. The KIAA1549-BRAF fusion was the most common alteration (21/37 patients) followed by AFAP1-NTRK2 (2/37) and TBLXR-PI3KCA (2/37) fusions that were observed at much lower frequencies. The most frequently mutated) genes were NOTCH1-3 (7/37), ATM (4/37), RAD51C (3/37), RNF43 (3/37), SLX4 (3/37) and NF1 (3/ 37). Interestingly, we identified a GOPC-ROS1 fusion in an 8-year-old patient whose tumor lacked BRAF alterations and histologically classified as low grade glioma. The patient underwent gross total resection (GTR). The patient is currently disease free. To our knowledge this is the first report of GOPC-ROS1 fusion in PLGG. Taken together, we reveal the genetic characteristics of pLGG patients can enhance diagnostics and therapeutic decisions. In addition, we identified a GOPC-ROS1 fusion that may be a biomarker for pLGG.