Abstract Details

Title Novel Fusion GNAI2::BRAF as Driver for Pilocytic Astrocytoma: A Case Report

Topic Neuro-oncology

Presentation(s) P4 - Poster Session 4 (11:45 AM-12:45 PM)

Poster/Presentation
Number 5-009

Objective To introduce a newly identified fusion, GNAI2::BRAF, as the oncogenic driver in a rare case of adult pilocytic astrocytoma

Background Pilocytic astrocytoma is a circumscribed astrocytic glioma that primarily affects children and young adults. These tumors are driven by alterations in the MAPK pathway, most commonly the KIAA1549::BRAF fusion, BRAF V600E mutation, and NF1 mutation. Other activating fusions involving BRAF have also rarely been reported.

Design/Methods Case Report.

Results We present the case of a 58-year-old right-handed female who presented with transient right forearm and paresthesia. MRI brain with and without contrast revealed a 1.4 cm non-enhancing T2 hyperintense lesion in the left frontal lobe. She underwent surgical resection. Histology showed a low-grade glial neoplasm with Rosenthal fibers. Initial molecular testing was negative for the KIAA1549::BRAF fusion, though RNA fusion analysis using a partner agnostic assay showed a GNAI2::BRAF fusion, which has not been previously reported. Methylation profiling by both the Heidelberg and NCI/Bethesda classifiers indicated a consensus match with supratentorial pilocytic astrocytoma. The patient had a gross total surgical resection, is clinically asymptomatic, and is being monitored by surveillance MRIs. Analysis of RNA sequencing data from a large cohort of low-grade glial tumors from our institution is in process to determine how common this fusion is.

Conclusions This case establishes GNAI2::BRAF as a rare oncogenic driver in pilocytic astrocytoma. Novel molecular pathology methods including a partner agnostic RNA fusion assay and methylome profiling were central to establishing this diagnosis.

Authors/Disclosures
Maria A. Minor, MD (Duke University) PRESENTER	Dr. Minor has nothing to disclose.
Gregory Chamberlin (Duke University)	No disclosure on file
Justin T. Low, MD, PhD (Duke University School of Medicine)	Dr. Low has nothing to disclose.
Karra Jones (Duke University)	No disclosure on file
Kevin Stevenson	No disclosure on file
William Jeck (Duke University School of Medicine)	No disclosure on file
Vanessa Smith (Duke University Health System)	No disclosure on file

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