Case Report: Clinicopathological and Genetic Features of IDH-Mutant Brainstem Glioma in Adults: Report of Five Cases

Fulminant hemorrhagic course of a thalamic H3 K27-altered diffuse midline glioma in an adult patient: illustrative case

BACKGROUND

H3 K27-altered diffuse midline gliomas (DMGs) are rare tumors, which are, regardless of their histological appearance, classified as World Health Organization grade 4 tumors. They are characterized by a diffuse growth pattern, midline anatomical location, and poor prognosis. Although DMGs occur predominantly in childhood, these tumors can also be found in young adults.

OBSERVATIONS

The authors present a case of a 29-year-old patient who was found unconscious with a Glasgow Coma Scale score of 4, along with abnormal extensor movements and bilateral middilated nonreactive pupils. Computed tomography revealed obstructive hydrocephalus due to an acute hemorrhage in a right thalamic lesion. To drain the hydrocephalus and relieve the ongoing central herniation, emergent placement of a right-sided, and later a left-sided, extraventricular drain was performed. Despite the postoperative resolution of hydrocephalus, the patient died shortly after because of the central brain herniation that had occurred. Brain autopsy revealed a H3 K27-altered DMG in the right thalamus.

LESSONS

Although typically described in the pediatric population and located in the pons, H3 K27-altered DMG should also be considered in young adult patients with midline lesions, particularly if they are located in the thalamus or brainstem. In rare cases, H3 K27-altered DMG may present with an acute tumor-related hemorrhage, leading to a fulminant clinical course.

H3K27-altered diffuse midline gliomas with MAPK pathway alterations: Prognostic and therapeutic implications

Large-scale sequencing led to the identification of driver molecular alterations such as FGFR1 and BRAF in occasional diffuse midline gliomas (DMGs) H3K27-mutant but their significance has not been completely explored. We evaluated these associations in our institutional cohorts. We searched our archives for H3K2M7-mutant gliomas and analyzed the co-occurring genetic alterations. The demographics, clinical information, and pathology were reviewed. Oncoplots and Kaplan-Meier survival curves were generated with the maftools R package. We identified 81 patients (age range 2-68, median 26), of which 79 (97%) were DMGs, and 2 were glioneuronal tumors. The 2 glioneuronal tumors (1 with BRAF fusion and 1 BRAF-V600E-mutant) were removed from the outcome analysis. Four cases had BRAF V600E mutation, 12 had FGFR1 hotspot mutations, and one each had KRAS and NRAS pathogenic mutations. The most common correlating anatomic location was the brainstem for the BRAF group and thalamus for the FGFR1group. Follow-up ranged from 0 to 78 months, average 20.4 months. The overall survival in FGFR1- and BRAF V600E-mutant DMGs was not statistically improved when compared with those that were wildtype. However, the possibility of targeted therapy argues for comprehensive sequencing of H3K27-altered gliomas.

[IDH-mutant brainstem glioma]

Diffuse midline gliomas are relatively rare in adults. Regardless of age, all diffuse midline gliomas are routinely examined in our Center for the presence of the H3F3A K27M gene mutation. However, we identified IDH-mutant brainstem glioma in a 42-year-old man for the first time.