CT and Multimodal MR Imaging Features of Embryonal Tumors with Multilayered Rosettes in Children

Abstract

Background and purpose: Embryonal tumors with multilayered rosettes, C19MC-altered, are brain tumors occurring in young children, which were clearly defined in the 2016 World Health Organization classification of central nervous system neoplasms. Our objective was to describe the multimodal imaging characteristics of this new entity.

Materials and methods: We performed a retrospective monocentric review of embryonal brain tumors and looked for embryonal tumors with multilayered rosettes with confirmed C19MC alteration. We gathered morphologic imaging data, as well as DWI and PWI data (using arterial spin-labeling and DSC).

Results: We included 16 patients with a median age of 2 years 8 months. Tumors were both supratentorial (56%, 9/16) and infratentorial (44%, 7/16). Tumors were large (median diameter, 59 mm; interquartile range, 48-71 mm), with absent (75%, 12/16) or minimal (25%, 4/16) peritumoral edema. Enhancement was absent (20%, 3/15) or weak (73%, 11/15), whereas intratumoral macrovessels were frequently seen (94%, 15/16) and calcifications were present in 67% (10/15). Diffusion was always restricted, with a minimal ADC of 520 mm²/s (interquartile range, 495-540 mm²/s). Cerebral blood flow using arterial spin-labeling was low, with a maximal CBF of 43 mL/min/100 g (interquartile range, 33-55 mL/min/100 g 5). When available (3 patients), relative cerebral blood volume using DSC was high (range, 3.5-5.8).

Conclusions: Embryonal tumors with multilayered rosettes, C19MC-altered, have characteristic imaging features that could help in the diagnosis of this rare tumor in young children.

Fig 1.

Brain imaging of patient 6. Axial plane MR images show a large heterogeneous right temporal tumor, with mass effect and midline shift. The tumor displays hypointensity on the T1-weighted image (A), hyperintensity on the T2-weighted image (C), and weak enhancement after contrast media injection (B). An intratumoral vessel is seen (B). Diffusion signal is high (D) with low ADC. Diffusion is also restricted in the right occipital lobe (D) because of an ischemic injury caused by compression of the posterior cerebral artery.

Fig 2.

Brain imaging of patient 11. Axial plane image on CT (A) shows a right thalamic mass with microcalcifications. The tumor displays hypointensity on the T1-weighted image (B), hyperintensity on the T2-weighted image (D), and weak nodular enhancement after contrast media injection (C). An intratumoral vessel is seen (C). Diffusion signal is high (E) with low ADC. Cerebral blood flow (F) is low (maximum, 46 mL/min/100 g) within the tumor.

Fig 3.

Brain imaging of patient 3. Sagittal plane (A–C) MR images show a large midline vermian tumor, with mass effect on the fourth ventricle causing hydrocephalus. The tumor displays hypointensity on the T1-weighted image (A), hyperintensity on the T2-weighted image (C), and no enhancement after contrast media injection (B). Diffusion signal is high (D) with low ADC.

Fig 4.

Brain imaging of patient 4. Sagittal plane image on CT (A) shows a pontine isodense mass. The tumor displays hypointensity on the T1-weighted image (C), hyperintensity on the T2-weighted image (B), and no enhancement after contrast media injection (D). Diffusion signal is high (E) with low ADC (F).