Embryonal Tumor with Multilayered Rosettes, C19MC-Altered: Clinical, Pathological, and Neuroimaging Findings.

Background And Purpose: Embryonal tumor with multilayered rosettes (ETMR), C19MC-altered, is a recently described, rare central nervous system tumor. To our knowledge, the imaging findings of this tumor have not been systematically evaluated in the neuroradiology literature. We present here the clinical, radiological, and pathological correlation of a case series of this very rare tumor, including the full range of anatomic compartment presentations (supratentorial, infratentorial, and spinal).

Methods: We retrospectively analyzed 7 (4M, 3F) pathologically-proven cases of ETMR referred to our institution between 2007 and 2017. We demonstrate the imaging characteristics of this tumor on CT and MRI with advanced imaging.

Results: All of the patients are children (ages 1-12). On MR imaging of ETMR, contrast enhancement is often heterogeneous and minimal if any, and there is no significant surrounding T2 fluid-attenuated inversion recovery (FLAIR) hyperintensity to suggest edema. The lesions were often expansile with no evidence of infiltration of the fiber tracks that were displaced by the tumor mass. Diffusion-weighted imaging often demonstrated restricted diffusion within ETMRs. On magnetic resonance spectroscopy (MRS), the choline/creatine (Cho/Cr) ratio is increased, with low N-acetylaspartate (NAA) or NAA/Cho ratio, typical of high-grade tumors.

Conclusion: We demonstrate the conventional and advanced imaging characteristics of ETMR, including MRS and diffusion tensor imaging, which, to our knowledge, have not been systematically evaluated in the radiology literature. The knowledge gained may potentially impact patient management, especially in inoperable cases and in locations where it is risky to perform a biopsy.