T2-FLAIR Mismatch Sign in Pediatric Low-Grade Glioma

Area of Science:

• Neuro-oncology
• Radiology
• Molecular Pathology

Background:

• Qualitative imaging features lack sensitivity and specificity for predicting molecular alterations in pediatric low-grade gliomas (pLGG).
• The T2-FLAIR mismatch sign is a known predictor for specific molecular alterations in adult gliomas.

Purpose of the Study:

• To evaluate the diagnostic significance of the T2-FLAIR mismatch sign in pediatric low-grade gliomas.
• To determine if the T2-FLAIR mismatch sign correlates with specific molecular subtypes of pLGG.

Main Methods:

• Retrospective analysis of pretreatment MR images from 349 pediatric patients (0-18 years) with histopathologically confirmed pLGG.
• Inclusion criteria included availability of molecular information and preoperative T2-weighted and FLAIR MRI sequences.
• Molecular data, including KIAA1549-BRAF fusion and BRAF p.V600E mutation, were assessed.

Main Results:

• The T2-FLAIR mismatch sign was present in 7.2% (25/349) of pediatric low-grade gliomas.
• None of the T2-FLAIR mismatch positive pLGGs exhibited BRAF p.V600E mutations.
• The T2-FLAIR mismatch sign was associated with rare molecular alterations in pLGG, not common BRAF alterations.

Conclusions:

• The T2-FLAIR mismatch sign is not observed in pediatric low-grade gliomas with common molecular alterations (BRAF p.V600E mutation or KIAA1549-BRAF fusion).
• The presence of the T2-FLAIR mismatch sign in pediatric low-grade gliomas suggests the possibility of rare molecular alterations.