Imaging Characteristics of Pediatric Diffuse Midline Gliomas with Histone H3 K27M Mutation

Abstract

Background and purpose: The 2016 World Health Organization Classification of Tumors of the Central Nervous System includes "diffuse midline glioma with histone H3 K27M mutation" as a new diagnostic entity. We describe the MR imaging characteristics of this new tumor entity in pediatric patients.

Materials and methods: We retrospectively reviewed imaging features of pediatric patients with midline gliomas with or without the histone H3 K27 mutation. We evaluated the imaging features of these tumors on the basis of location, enhancement pattern, and necrosis.

Results: Among 33 patients with diffuse midline gliomas, histone H3 K27M mutation was present in 24 patients (72.7%) and absent in 9 (27.3%). Of the tumors, 27.3% (n = 9) were located in the thalamus; 42.4% (n = 14), in the pons; 15% (n = 5), within the vermis/fourth ventricle; and 6% (n = 2), in the spinal cord. The radiographic features of diffuse midline gliomas with histone H3 K27M mutation were highly variable, ranging from expansile masses without enhancement or necrosis with large areas of surrounding infiltrative growth to peripherally enhancing masses with central necrosis with significant mass effect but little surrounding T2/FLAIR hyperintensity. When we compared diffuse midline gliomas on the basis of the presence or absence of histone H3 K27M mutation, there was no significant correlation between enhancement or border characteristics, infiltrative appearance, or presence of edema.

Conclusions: We describe, for the first time, the MR imaging features of pediatric diffuse midline gliomas with histone H3 K27M mutation. Similar to the heterogeneous histologic features among these tumors, they also have a diverse imaging appearance without distinguishing features from histone H3 wildtype diffuse gliomas.

Fig 1.

Diffuse midline gliomas within the posterior fossa. A, FLAIR, T1 postgadolinum, and ADC maps of infratentorial diffuse gliomas demonstrate 2 distinct appearances, with the first type being centered within the pons with expansion of the pons and engulfment of the basilar artery (14 patients). The second type was centered within the vermis and cerebellar peduncle with extension into the fourth ventricle and involvement of the posterior pons (5 patients). B, Imaging features of both the histone H3 K27M and wildtype tumors were heterogeneous with respect to necrosis, patterns of enhancement, edema, and infiltrative features. Black bars represent the presence of the feature; white bars represent lack of the feature.

Fig 2.

Imaging of tumor progression in histone H3 K27M mutant tumors. FLAIR and T1-weighted contrast-enhancing images demonstrate local infiltrative (A) and CSF-based progression (B) in histone H3 K27M mutants.

Fig 3.

Imaging of tumor progression in histone H3 wildtype tumors. FLAIR and T1-weighted contrast-enhancing images demonstrate mixed local infiltrative progression with CSF-based metastatic disease (A) and local infiltrative progression (B).

Fig 4.

Imaging of midline gliomas centered within the thalamus. Midline gliomas with histone H3 K27M mutation centered within the thalamus had 2 specific imaging presentations, with (A) and without (B) contrast enhancement. Three patients had contrast enhancement, and 3 patients did not. C, Imaging features within the thalamic gliomas based on the presence of the histone H3 K27M mutation. Black bars represent the presence of the feature; white bars represent lack of the feature.

Fig 5.

Imaging of cervical spine histone H3 K27M mutant gliomas. T2-weighted and postcontrast T1-weighted imaging of cervical spine glioblastomas that presented with subependymal metastatic disease and evidence of significant progression involving the subependymal surfaces of the lateral ventricles and the folia of the cerebellum at 5 months after initial diagnosis.