Review Article “Tumor-like” lesions of the pediatric brain Andrea Poretti a,b, *, Majid Chalian a , Avner Meoded a and Thierry A.G.M. Huisman a a Division of Pediatric Radiology, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA b Division of Pediatric Neurology, University Children’s Hospital, Zurich, Switzerland Received 14 November 2012 Revised 14 November 2012 Accepted 3 October 2012 Abstract. Distinguishing “real” neoplastic tumors from “tumor-like” lesions of the central nervous system is important to treat chil- dren properly, to predict outcome and prognosis, and to avoid unnecessary medical treatment or surgical interventions. Neuroimaging plays a key role in the correct differentiation between both entities. Pediatric radiologists should be aware of all non-neoplastic lesions that may mimic tumors. High-end anatomic and advanced magnetic resonance imaging as well as the correlation with history and clinical findings facilitate differentiation between both entities. The aim of this pictorial review is to review the neuroimaging man- ifestations of the most common “tumor-like” lesions affecting the pediatric brain. Keywords: Tumor-like lesions, central nervous system, pediatrics, MRI 1. Introduction Neuroimaging features suggesting a tumor include a focal density or signal alteration displacing or infiltrating brain structures. Contrast enhancement and perifocal edema may or may not be present. Unfortunately, non-neoplastic lesions may have similar features (Figs. 1 and 2) [1]. Differentiation between tumors and “tumor- like” lesions is important for treatment, outcome, and prognosis. Neoplasms need an aggressive treatment, while “tumor-like” lesions may be treated more conserva- tively. Misinterpretation may lead to a delay of treatment of tumors or may result in over-treatment of “tumor-like” lesions. We present the neuroimaging features of common pediatric “tumor-like” lesions. 2. Infections Brain abscesses may occur as complication of a menin- goencephalitis, from direct extension from a nearby focus (e.g. sinusitis or otitis), from penetrating head traumas, or from hematogenous spread from an extracranial infection (septic emboli) (Fig. 3). Brain abscesses typically present as round, space-occupying masses with extensive perifo- cal edema and a strong, peripheral, ring-like contrast enhancement and may mimic high-grade gliomas [2] (Fig. 4). Diffusion weighted imaging (DWI) facilitates differentiation between abscess (restricted diffusion) and necrotic high-grade tumors (increased diffusion) (Fig. 4). Additionally, 1 H-magnetic resonance spectro- scopy ( 1 H-MRS) may also be helpful in differentiating abscesses from high- and low-grade tumors. Given the lack of normal brain tissue, basic brain metabolites such as N-acetyl aspartate (NAA), choline (Cho), and creatine (Cr) are lacking within the abscess, whereas other meta- bolites such as lactate, lipids, amino acids, acetate, and succinate may be present [3]. In brain tumors NAA, Cho, and Cr are typically present and high-grade tumors *Corresponding author: Dr. Andrea Poretti, Division of Pediatric Radiology, Russell H. Morgan Department of Radiology and Radiolo- gical Science, The Johns Hopkins School of Medicine, 600 North Wolfe Street, Nelson B-173. Baltimore, MD 21287-0842, USA. Tel.: +1 410 614 3772; Fax: +1 410 502 3633; E-mail: aporett1@jhmi.edu. Journal of Pediatric Neuroradiology 1 (2012) 261–267 DOI 10.3233/PNR-2012-033 IOS Press 261 1309-6680/12/$27.50 © 2012 – IOS Press and the authors. All rights reserved