Abstract
Pilocytic astrocytoma (PA) is the most frequently encountered glial tumor (glioma or astrocytoma) in children. Recent studies have identified alterations in the BRAF serine/threonine kinase gene as the likely causative mutation in these childhood brain tumors. The majority of these genetic changes involve chromosome 7q34 tandem duplication, resulting in aberrant BRAF fusion transcripts. In this paper, we describe a novel KIAA1549:BRAF fusion transcript in a sporadic PA tumor associated with increased ERK activation and review the spectrum of BRAF genetic alterations in this common pediatric low-grade central nervous system neoplasm.
Highlights
Pilocytic astrocytomas are the most common nonmalignant brain tumor in the pediatric population
We describe a novel KIAA1549:BRAF fusion transcript in a sporadic Pilocytic astrocytoma (PA) tumor associated with increased ERK activation and review the spectrum of BRAF genetic alterations in this common pediatric low-grade central nervous system neoplasm
The inclusion of this specific genetic alteration to the growing list of BRAF molecular changes supports a model in which fusion events that maintain the BRAF open reading frame and include the BRAF protein sequences encoded by exons 11–18 (BRAF kinase domain) are potentially tumorigenic
Summary
Pilocytic astrocytomas are the most common nonmalignant brain tumor in the pediatric population. Children with the Neurofibromatosis type 1 (NF1) inherited cancer predisposition syndrome are prone to the development of these glial cell neoplasms, such that 15–20% of affected individuals will develop gliomas involving the optic pathway, hypothalamus, and brainstem [1] Molecular analysis of these tumors has revealed biallelic inactivation of the NF1 tumor suppressor gene, resulting in loss of NF1 protein (neurofibromin) expression. The most frequently encountered genetic alteration is a tandem duplication of the BRAF gene on chromosome 7q34, leading to fusion of the KIAA1549 gene to the carboxyl terminal region of the BRAF gene containing the kinase domain This molecular change has been reported in 50–65% of sporadic pilocytic astrocytoma and is more frequent in cerebellar (∼80%) tumors. We describe a novel KIAA1549-BRAF fusion event in a sporadic pediatric pilocytic astrocytoma
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