Learning Objectives
To review the magnetic resonance imaging appearances of paediatric supratentorial primitive neuroectodermal tumours and highlight the characteristic imaging features that assist in diagnosis and differentiation from other paediatric brain tumours.
Background
Primitive neuroectodermal tumours (PNET) refers to a heterogeneous group of undifferentiated malignant tumours of the central nervous system (CNS). The World Health Organisation (WHO) classifies PNET as grade IV neoplams.
Histologically,
it is an extremely cellular tumour with small round blue cells of neural crest origin with scanty cytoplasm and variable sized nuclei [1]. However,
the designation of PNET is controversial. Medulloblastoma (MB-PNET) is the prototype of infratentorial PNET and is the most common paediatric CNS tumour (15-25%) [2].
Supatentorial PNET (S-PNET) is rare,
consisting...
Imaging Findings OR Procedure Details
MRI is preferred imaging modality. Standard sequences should include T1,
T2,
FLAIR,
T2*/SWI,
DWI and T1 post contrast of the brain. The entire spine should also be examinated as leptomeningeal metastases are common in S-PNET. The spine protocol should include T1,
T2 and T1 post contrast. Spectroscopy is optional.
General Appearances
The general appearances of S-PNET is a large well marginated hemispheric mass effacing the ventricles [3,5]. Its signal characteristics usually is iso to hypo-intense compared with grey matter on both T1 and T2 with...
Conclusion
S-PNET is a rare,
high-grade CNS malignancy of young children.
Characteristic MR appearances including positive DWI and lack of peritumoural oedema are helpful in suggesting the diagnosis of S-PNET,
and differentiating it from other more common paediatric CNS neoplasms
References
1.Kleihues P,
Burger PC,
Scheithauer BW.
Histological classification of CNS tumours.
In: Sobin LH,
editor. Histological typing of tumours of the central nervous system.
2nd ed.
Berlin: Springer-Verlag; 1993.
p.1-105.
2.Klisch J,
Husstedt H,
Hennings S,
et al.
Supratentorial primitive neuroectodermal tumours: diffusion-weighted MRI. Neuroradiology 2000;42:393-8.
3.Chawla A,
Emmanuel JV,
Seow WT,
et al.
Paediatric PNET: pre-surgical MRI features.
Clinical Radiology 2007;62:43-52.
4.Dirks PB,
Harris L,
Hoffman HJ,
et al.
Supratentorial primitive neuroectodermal tumors in children.
J Neuro-Oncol 1996;29:75-84.
5.Dai,
AI,
Backstrom JW,
Burger PC,...