AB013. Infantile brainstem high grade glioma: a case report.

Background: Congenital infantile brainstem high-grade gliomas (HGGs) are extremely rare. Given the limited literature characterizing this disease, management of these tumors remains challenging. Brainstem HGGs are generally associated with extremely poor prognosis. Limited reports of spontaneous regression of radiologically diagnosed infantile brainstem tumors exist in published literature. We aim to report a unique case of spontaneous regression of a rare infantile HGG brainstem glioma and to review the current literature.

Case description: In this case report, we document the first histologically proven congenital brainstem HGG with molecular characteristics that did not fall under any previously well-defined pediatric brain tumor classifications. The patient is a full-term female delivered uneventfully via normal vaginal delivery with unremarkable antenatal and fetal abnormality scans. Neuroimaging revealed a relatively focal dorsally located pontomedullary tumor. She subsequently underwent suboccipital craniotomy and biopsy of the lesion. Formal histopathology revealed features consistent with HGG. Methylation profiling classified the neoplasm closest to either "glioblastoma, IDH wildtype, subclass midline" or "pediatric type diffuse HGG". The patient's post-operative recovery was uneventful. The initial plan was to consider safe surgical debulking when the child reaches 6 months of age. However, subsequent neuroimaging revealed spontaneous tumor regression after biopsy, up to 2 years of age. A review of the literature was also performed to identify previously reported infantile brainstem HGGs and the management for such tumors.

Conclusions: Our case highlights the value of performing histopathological confirmation to guide management and the possible existence of a subcategory of a congenital brainstem HGG with better prognosis.