Rev Esp Med Nucl Imagen Mol. 2013;32(6):394–396 Clinical note Primary central nervous system lymphoma with lymphomatosis ceribri in an immunocompetent child: MRI and 18 F-FDG PET-CT findings Tarun K. Jain a , Punit Sharma a , Sudhir K.C. Suman a , Nauroze A. Faizi a,b , Chandrasekhar Bal a , Rakesh Kumar a,∗ a Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India b Department of Radiodiagnosis, All India Institute of Medical Sciences, New Delhi, India a r t i c l e i n f o Article history: Received 19 February 2013 Accepted 3 April 2013 Available online xxx Keywords: Lymphoma Central nervous system Lymphomatosis cerebri Magnetic resonance imaging PET-CT a b s t r a c t Primary central nervous system lymphoma (PCNSL) is extremely rare in immunocompetent children. We present the magnetic resonance imaging (MRI) and 18 F-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography-computed tomography (PET-CT) findings of such a case in a 14-year old immunocompetent boy. In this patient, PCNSL was associated with lymphomatosis cerebri. Familiarity with the findings of this rare condition will improve the diagnostic confidence of the nuclear radiologist and avoid misdiagnosis. © 2013 Elsevier España, S.L. and SEMNIM. All rights reserved. Linfoma primario del sistema nervioso central con linfomatosis cerebri en un ni˜ no inmunocompetente: hallazgos de la MRI y 18 F-FDG PET-TC Palabras clave: Linfoma Sistema nervioso central Linfomatosis cerebri Resonancia magnética PET-TC r e s u m e n El linfoma primario del sistema nervioso central (LPSNC) es extremadamente raro en ni˜ nos inmunocom- petentes. Presentamos los hallazgos de la imagen de resonancia magnética (MRI) y de tomografía por emisión de positrones-tomografía computarizada (PET-TC) con 18 F-FDG en un ni˜ no inmunocompetente de 14 a˜ nos de edad. En este paciente el LPSNC se asoció con linfomatosis cerebri. Estar familiarizado con los hallazgos de esta rara afectación mejorará la confianza diagnóstica del médico nuclear y evitará un diagnóstico erróneo. © 2013 Elsevier España, S.L. y SEMNIM. Todos los derechos reservados. Introduction Primary central nervous system lymphoma (PCNSL) is a rare tumour accounting for 3–5% of primary brain tumours in adults. They are extremely rare in children. 1 PCNSL most often presents as a solitary, isolated lesion in immunocompetent patients. Rarely, the disease presents as a diffuse, infiltrating condition without forma- tion of a cohesive mass, a pattern called ‘lymphomatosis cerebri’. PCNSL are extranodal malignant lymphomas that arise within the brain, eyes, leptomeninges, or spinal cord in the absence of systemic lymphoma at the time of diagnosis. Epidemiological data have shown a continual increase over past decades in the immunocom- petent population, whereas the incidence seems to be decreasing in immunocompromised patients, mainly due to development of highly active anti-retroviral therapies. 2 We here describe a case of PCNSL with lymphomatosis cerebri in an immunocompetent child and discuss the magnetic resonance imaging (MRI) and ∗ Corresponding author. E-mail address: rkphulia@yahoo.com (R. Kumar). 18 F-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography- computed tomography (PET-CT) features. Clinical case A 14-year old male child was admitted with complaints of recur- rent rashes, sore throat and fever of 4-month duration. He also had cognitive dysfunction with concomitant gait abnormalities (ataxic gait) and recurrent focal seizures for the last 2 months. His rou- tine blood parameters including electrolytes, urea, creatinine, CRP, transaminases, ESR were within normal range. Serology for human immunodeficiency virus (HIV) was negative. Cerebrospinal fluid (CSF) examination results were also normal with few lymphocytes. MRI of the brain revealed enhancing confluent mass lesions in the bilateral thalami and corpus callosum (Fig. 1). In addition, also noted were diffuse hyperintense lesions in the white matter of both cerebral hemispheres. There was no evidence of restricted dif- fusion. The differential diagnoses on MRI were malignant glioma and PCNSL. For further evaluation of the lesions 18 F-FDG PET-CT was done. PET-CT showed ill-defined hyperdense lesions involv- ing predominantly the periventricular white matter and the corpus callosum with mass effect (midline shift towards left side) and 2253-654X/$ – see front matter © 2013 Elsevier España, S.L. and SEMNIM. All rights reserved. http://dx.doi.org/10.1016/j.remn.2013.04.002 2253-8089/$