MRI Evaluation of Non-Necrotic T2-Hyperintense Foci in Pediatric Diffuse Intrinsic Pontine Glioma

Abstract

Background and purpose: The conventional MR imaging appearance of diffuse intrinsic pontine glioma suggests intralesional histopathologic heterogeneity, and various distinct lesion components, including T2-hypointense foci, have been described. Here we report the prevalence, conventional MR imaging semiology, and advanced MR imaging features of non-necrotic T2-hyperintense foci in diffuse intrinsic pontine glioma.

Materials and methods: Twenty-five patients with diffuse intrinsic pontine gliomas were included in this study. MR imaging was performed at 3T by using conventional and advanced MR imaging 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 brain stem. 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. Volume transfer coefficient values in T2-hyperintense foci were lower than those in T2-hypointense (P = .0005) or necrotic T2-hyperintense (P = .0348) foci.

Conclusions: Non-necrotic T2-hyperintense foci are common, distinct lesion components within diffuse intrinsic pontine gliomas. Advanced MR imaging 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 pathophysiologic changes remain unclear; therefore, these foci may correspond to a poorly understood biologic event in tumor evolution.

© 2016 by American Journal of Neuroradiology.

Figures

Fig 1.

Axial MR images centered on the pons and showing non-necrotic T2HrF (long arrow). T2-weighted image (A), ADC map (B), T1-weighted postcontrast subtraction image (C), and CBV map (D). These images show a well-defined, fairly voluminous T2HrF within the left hemipons (a smaller similar lesion may be present on the right side, too), which is associated with mass effect, slightly increased signal in ADC (B), lack of contrast enhancement after IV gadolinium injection (C), and moderately increased CBV (D).

Fig 2.

Axial (A) and sagittal (B) T2-weighted MR images of a DIPG with both non-necrotic T2HrF (arrowhead) and T2HoF (long arrow).

Fig 3.

Boxplots of ADC, rCBV, Ktrans, and ve for the different ROI types analyzed in DIPG. The y-axis of boxplots was rescaled for rCBV, Ktrans, and ve. Error bars represent SDs. Statistical differences between groups (P < .05) are signified as follows: The asterisk indicates normal brain stem, ¥, T2HoF; ‡, necrotic T2HrF; §, edema.

Fig 4.

Feature comparison of the 4 ROIs. A, Normal brain stem. B, A non-necrotic T2HrF is a well-circumscribed intratumoral area exhibiting high T2 signal and is often associated with local mass effect on surrounding structures, shown by splaying transverse pontocerebellar fibers. C, T2HoF are characterized by low T2 signal and are locally expansile. D, Necrotic T2HrF exhibit irregular margins, central T2 hypersignal, peripheral T2 hyposignal, and postcontrast signal enhancement. On the basis of their advanced MR imaging features, we speculate that non-necrotic T2HrF, T2HoF, and necrotic T2HrF, while possibly coexisting, may indicate sequential steps in the evolution of tumor cell populations (clones).