Morphological and Molecular Characterization of Infant-Type Hemispheric Glioma

To characterize the clinical, histopathological, and molecular features of infant-type hemispheric glioma (IHG) and explore any overlaps it might have with other types of pediatric gliomas.

Data from the Children's Brain Tumor Network (CBTN) were analyzed (last accessed in January 2025), with a focus on patients aged 0-4 years with gliomas, glioneuronal tumors, or ependymomas. This analysis encompassed the clinical, histological, and molecular profiles of the cases, including those with recurrent tumors. The study scrutinized the tumor circumscription, grading features, and molecular alterations, along with the Methylation Class, using methylation profiling via the Heidelberg v12.5 and v12.8 classifiers.

IHG is predominantly well-circumscribed, but recurrence may lead to infiltrative growth. Novel findings include the acquisition of additional genetic alterations in recurrent IHG, which alters prognosis. One case exhibited progression to a pleomorphic xanthoastrocytoma-like profile, while another acquired glioblastoma-like infiltrative pattern and TP53 mutations, associated with a more aggressive course. Distinguishing IHG from desmoplastic infantile ganglioglioma/astrocytoma (DIG/A) and Pediatric High-Grade Gliomas (pHGG) remains challenging, particularly in the absence of molecular data.

This study emphasizes the heterogeneity of IHG and underscores the necessity for molecular surveillance in recurrent instances. The findings aid in refining diagnostic criteria and understanding the prognostic implications of genetic alterations in IHG.