BACKGROUND Neuronal and mixed neuro-glial tumors of the central nervous system (CNS) are relatively rare. Dysembryoplastic neuroepithelial tumor (DNET) is a benign, rare, slow-growing tumor, but in many cases is associated with intractable epilepsy. OBJECTIVE To report the experience with DNET at a single free-standing children’s institution. METHODS A retrospective chart review of 24 patients with confirmed DNET between 2001 and 2019 was performed. Data was collected on clinical characteristics, tumor location, surgical management, histopathological and molecular findings, and outcomes. RESULTS Mean age at diagnosis was 10 years (range 2 to 19 years), with female predominance (54.2%). Most common presenting symptoms were seizures (79.2%) and headaches (12.5%). Location of the tumor was temporal (29.2%), frontal (25.0%), parietal (16.7%), cerebellar (12.5%) and occipital (4.2%). A gross total resection was achieved in half the cases. Recurrence occurred in 4 patients (16.7%), all of whom had subtotal resections. The average follow up since diagnosis was 4.6 years (range 0.3 to 14 years). Nineteen patients presented with seizures, of which 63.2% were seizure free after surgery. The samples with molecular genetic testing (microarrays or FISH), were all normal except one patient positive for BRAF V600E mutation. CONCLUSIONS This is the first and largest review of pediatric DNETs in the last 10 years. Despite majority of patients having a favorable outcome after surgery, a subset of patients remains symptomatic. As molecular mechanisms in DNET remain unknown, future aim is to describe the molecular characteristics of our DNET population, and correlate with outcomes.
BACKGROUND Numerous variant BRAF genetic alterations have been associated with malignancies. BRAF activating fusions/mutations are frequently present in low grade gliomas. BRAF intragenic deletions have been reported in melanoma, but have not previously been reported in gliomas. OBJECTIVE To report a BRAF intragenic deletion in a pediatric patient with recurrent low-grade glioma. RESULTS A 3-year-old female underwent a complete resection of a posterior fossa pilocytic astrocytoma. She had recurrences at age 4, and then at age 9; pathology was consistent with pilocytic astrocytoma. Microarray analysis on sample from the first recurrence showed one region of loss encompassing 86 Kbp within the BRAF gene. The deletion breakpoints are within intron 1 and 9, resulting in loss of exons 2 through 9, inclusive. This has been previously described melanoma, but appears to be a novel finding in glioma. It is hypothesized that, since the loss retains the kinase and ATP binding pocket domains but deletes the N-terminal conserved region 1 and 2 (CR1, CR2) of the BRAF gene, it is likely functionally similar to the loss and activation resulting from the more usually described KIAA1549 and BRAF gene fusion. CONCLUSION This is the first BRAF intragenic deletion involving exons 2–9 reported in a glioma. Although 86kbp is small using whole genome microarray technology, it is large using sequencing strategies, and a targeted sequencing approach to investigate the BRAF gene would not readily identify this deletion. It is speculated that the deletion may be under ascertained in the pediatric population.
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