Abstract
PurposeThe entity ‘diffuse midline glioma, H3 K27M-mutant (DMG)’ was introduced in the revised 4th edition of the 2016 WHO classification of brain tumors. However, there are only a few reports on magnetic resonance imaging (MRI) of these tumors. Thus, we conducted a retrospective survey focused on MRI features of DMG compared to midline glioblastomas H3 K27M-wildtype (mGBM-H3wt).MethodsWe identified 24 DMG cases and 19 mGBM-H3wt patients as controls. After being retrospectively evaluated for microscopic evidence of microvascular proliferations (MVP) and tumor necrosis by two experienced neuropathologists to identify the defining histological criteria of mGBM-H3wt, the samples were further analyzed by two experienced readers regarding imaging features such as shape, peritumoral edema and contrast enhancement.ResultsThe DMG were found in the thalamus in 37.5% of cases (controls 63%), in the brainstem in 50% (vs. 32%) and spinal cord in 12.5% (vs. 5%). In MRI and considering MVP, DMG were found to be by far less likely to develop peritumoral edema (OR: 0.13; 95%-CL: 0.02–0.62) (p = 0.010). They, similarly, were associated with a significantly lower probability of developing strong contrast enhancement compared to mGBM-H3wt (OR: 0.10; 95%-CL: 0.02–0.47) (P = 0.003).ConclusionDespite having highly variable imaging features, DMG exhibited markedly less edema and lower contrast enhancement in MRI compared to mGBM-H3wt. Of these features, the enhancement level was associated with evidence of MVP.
Highlights
Diffuse intrinsic pontine gliomas (DIPG) are the most common cause of brain tumor-related death in children [1]
In magnetic resonance imaging (MRI) and considering microvascular proliferation (MVP), DMG were found to be by far less likely to develop peritumoral edema (OR: 0.13; 95%-CL: 0.02–0.62) (p = 0.010)
They, were associated with a significantly lower probability of developing strong contrast enhancement compared to mGBM-H3wt (OR: 0.10; 95%-CL: 0.02– 0.47) (P = 0.003)
Summary
Diffuse intrinsic pontine gliomas (DIPG) are the most common cause of brain tumor-related death in children [1]. Since tumors harboring H3 K27M mutations were frequently identified in the spinal cord, brainstem and diencephalon, and the patients showed a poor prognosis regardless of the tumor’s morphological appearance [1,7,8,9,10,11], they were defined as a new entity called ‘diffuse midline gliomas, H3-K27M-mutant’ (DMG) in the revised 4th edition of the WHO classification of brain tumors of 2016 [12]. According to the criteria of the WHO classification of brain tumors, glioblastomas (GBM) are defined as malignant astrocytomas with necrosis and/or microvascular proliferation (MVP) [12]. The definition criteria of the WHO classification for DMG do not enforce the detection of necrosis and/or vascular proliferation, so that a minor group of DMG can histopathologically manifest as a lower-graded glioma without considering H3 K27M mutations [12]
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