Pediatric-Type Diffuse Low-Grade Gliomas with MYB Alterations: Neuroimaging of the Diffuse Astrocytomas, MYB- or MYBL1-Altered

Abstract

BACKGROUND AND PURPOSE: Diffuse astrocytoma, MYB- or MYBL1-altered (DA-MYB) is a new tumor type in the family of pediatric-type diffuse low-grade gliomas and is genetically related to angiocentric glioma. Imaging features of DA-MYB, are less well-known. During our clinical work, in a subset of our patients, we identified a relatively characteristic imaging pattern consisting of a large, diffuse, hemispheric tumor with displaced central vessels, which we termed the “fireworks sign.” Therefore, the purpose of this work was to describe the frequency of this sign and any additional imaging characteristics in a large patient cohort. MATERIALS AND METHODS: This international retrospective study included 40 patients from 7 countries. We recorded clinical, genetic, and standard radiologic features, focusing on the presence of the fireworks sign but also on the presence or absence of a mismatch between T2WI and FLAIR and a FLAIR rim, which have both been reported in these patients. RESULTS: Most tumors were unilateral and located in the cerebral hemispheres (most frequently in the parietal, temporal, and frontal lobes), hypointense on T1WI, and hyperintense on T2WI. No tumor showed diffusion restriction. The fireworks sign was present in 16 patients. Other features included the T2 FLAIR mismatch (24 cases), FLAIR rim (18 cases), necrosis (5 cases), and enhancement (5 cases). Tumor volume was significantly associated with the fireworks sign (P ¼ .01) and T2 FLAIR mismatch (P ¼ .005). CONCLUSIONS: Imaging features of DA-MYB in children are variable, and the fireworks sign was identified only in a subset of patients. It was usually present in patients with large hemispheric tumors but was also observed in brainstem lesions. Diffusion restriction was consistently absent and enhancement infrequent. A T2 FLAIR mismatch was seen in .50% of patients.