Abstract
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. 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. 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. 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.
Highlights
BACKGROUND AND PURPOSEThe 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
Among 33 patients with diffuse midline gliomas, histone H3 K27M mutation was present in 24 patients (72.7%) and absent in 9 (27.3%)
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
Summary
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. We identified 33 pediatric patients with diffuse midline gliomas that were tested for the presence of the histone H3 K27M mutation and underwent primary work-up or tumor board review at our institution. This retrospective study was performed in compliance with Health Insurance Portability and Accountability Act regulations and was approved by our institutional review board. Formalin-fixed, paraffin-embedded tumor tissue was analyzed by a University of California, San Francisco neuropathologist (D.A.S.). Immunohistochemistry for histone H3 K27M mutant protein was performed by using a rabbit polyclonal antibody (ABE419; EMD Milipore, Billerica, Massachusetts), which detects histone H3.3 and H3.1 tails, as previously described.[6,9] Immunohistochemical staining was performed in a BenchMark XT Auto Stainer (Ventana Medical Systems, Tucson, Arizona) by using the Cell Conditioning 1 (Ventana Medical Systems) antigen retrieval buffer for 30 minutes at 95°C, incubation with a primary antibody at 1:500 dilution for 32 minutes, and the ultraView Universal DAB Detection Kit (Ventana Medical Systems).
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