Background and Purpose
The conventional MRI appearance of diffuse intrinsic pontine glioma suggests intralesional histopathological heterogeneity, and various distinct lesion components, including T2-hypointense foci, have been described. Here we report the prevalence, conventional MRI semiology, and advanced MRI features of non-necrotic T2-hyperintense foci within diffuse intrinsic pontine glioma.
Materials and Methods
Twenty-five patients with diffuse intrinsic pontine glioma were included in this study. MRI studies were performed at 3T by using conventional and advanced MRI sequences. Perfusion (CBV), vascular permeability (ve, Ktrans) and diffusion (ADC) metrics were calculated and used to characterize non-necrotic T2-hyperintense foci in comparison with other lesion components, namely necrotic T2-hyperintense foci, T2-hypointense foci, peritumoral edema, and normal brainstem. Statistical analysis was performed by using Kruskal–Wallis and Wilcoxon rank sum tests.
Results
Sixteen non-necrotic T2-hyperintense foci were found in 12 tumors. In these foci, ADC values were significantly higher than those in either T2-hypointense foci (P=.002) or normal parenchyma (P=.0002), and relative CBV values were significantly lower than those in either T2-hypointense (P=.0002) or necrotic T2-hyperintense (P=.006) foci. Ktrans values in T2-hyperintense foci were lower than those in T2-hypointense (P=.0005) or necrotic T2-hyperintense (P=.0348) foci.
Conclusion
Non-necrotic T2-hyperintense foci are common, distinct lesion components within diffuse intrinsic pontine glioma. Advanced MR data suggest low cellularity and an early stage of angioneogenesis with leaky vessels resulting in expansion of the extracellular space. Because of the lack of biopsy validation, the underlying histoarchitectural and pathophysiological changes remain unclear; therefore, these foci may correspond to a poorly understood biological event in tumor evolution.