CASE 14123 Published on 16.11.2016

Embryonal tumor with multilayered rosettes


Paediatric radiology

Case Type

Clinical Cases


Delgado-Moraleda JJ, Menor-Serrano F, Álvarez-Martínez V, Albertz-Arévalo N, Nersesyan N, Salvador-García J

Hospital La Fe,
Valencia, Spain;

20 months, female

Area of Interest Anatomy, Neuroradiology brain, Paediatric ; Imaging Technique MR, MR-Diffusion/Perfusion, CT, CT-High Resolution
Clinical History
A 20-month-old female presented to hospital for the third time in 5 days because of vomiting, with poor response to treatment. She was also sleepy and apathetic. Blood tests were normal. A cranial non-contrast CT was performed.
Imaging Findings
Non-contrast CT showed a well-demarcated rounded mass in the infratentorial midline affecting the cerebellum and the fourth ventricle, in close connection to the dorsal brainstem. The tumour was solid and hyperattenuated compared to cerebellar grey matter, with punctate calcifications and a few small necrotic cysts. It was difficult to assess the origin of the tumour as arising from cerebellum or fourth ventricle.

On MRI, T1-weighted sagittal images suggested a cerebellar origin with extension through both the fourth ventricle and the foramen magnum. On T2-weighted axial images, extension through right foramen of Luschka was observed. The tumour showed T1 hypointensity, T2 isointensity, and low signal elements on T2* images due to the presence of both calcium and blood. Diffusion-weighted images showed slight hyperintensity. After contrast administration, heterogeneous enhancement of the tumour was observed. Neither cranial nor spinal meningeal extension was evident.
This case illustrates the differential diagnosis of infratentorial midline tumours in patients under 2 years old. Accurate location and extension of the tumour can narrow the diagnosis [1].

If the lesion originates from the cerebellum, a cleavage plane with the floor of the fourth ventricle is usually observed. Then the most likely diagnoses are medulloblastoma and pilocytic astrocytoma. At this age we would also consider atypical teratoid / rhabdoid tumor and pilomyxoid astrocytoma.

If the lesion arises from the floor of the fourth ventricle, one would expect a better cleavage plane with the cerebellum. This finding is usually seen in ependymomas because they stem from the floor of the fourth ventricle, except the "roof" type which arises from inferior vermis/ medullary velum. The diagnosis of ependymoma is also supported by tumoral extension through the foramina of Luschka and Magendie.

In our case the large size of the lesion makes it difficult to identify its origin. The discrete extension through the lateral and caudal apertures of the fourth ventricle suggests ependymoma [2].

Non-contrast CT tumour hyperattenuation and iso-intensity on T2-weighted images compared to cerebellar grey matter suggest a higher cellularity tumour. Despite these findings, the tumour shows only slight restriction on MRI diffusion-weighted images.

High attenuation on CT suggests medulloblastoma or atypical teratoid/rhabdoid tumour. However, the solid component of pilocytic and pilomyxoid astrocytomas are usually hypoattenuated. Ependymoma shows an intermediate attenuation. Calcification and haemorrhagic foci can be observed in ependymomas [3].

Therefore, a differential diagnosis was established between cerebellar vermis medulloblastoma and ependymoma of the fourth ventricle. Atypical teratoid/rhabdoid tumour could not be excluded because of the age group.

The patient underwent surgery with complete tumour resection. Pathological diagnosis of surgical specimen was embryonal tumour with abundant neuropil and true rosettes (ETANTR).

According to the most recent classification of tumours of the central nervous system, developed by WHO in 2016 [4], the diagnosis would be embryonal tumour with multilayered rosettes (ETMR).

This new group includes medulloepithelioma, ependymoblastoma, and the embryonal tumour with abundant neuropil and true rosettes (ETANTR) in the previous classification. These three different tumors share a C19MC alteration, and so they are now considered in the same group. The term "PNET" has been removed from new WHO classification.

If C19MC alterations are not found, the tumour should be diagnosed as "embryonal tumour with multilayered rosettes, NOS" or "medulloepithelioma", depending on histological findings.
Differential Diagnosis List
Embryonal tumor with multilayered rosettes
Atypical teratoid / rhabdoid tumour
Pilocytic astrocytoma
Pilomyxoid astrocytoma
Final Diagnosis
Embryonal tumor with multilayered rosettes
Case information
DOI: 10.1594/EURORAD/CASE.14123
ISSN: 1563-4086