ORIGINAL ARTICLE [ 18 F]FDG PET/CT in the diagnosis of malignant peripheral nerve sheath tumours in neurofibromatosis type-1 Victoria S. Warbey & Rosalie E. Ferner & Joel T. Dunn & Eduardo Calonje & Michael J. O’Doherty Received: 26 August 2008 / Accepted: 28 November 2008 / Published online: 14 January 2009 # Springer-Verlag 2009 Abstract Purpose The detection of malignant peripheral nerve sheath tumours (MPNSTs) in patients with neurofibromatosis 1 (NF1) remains a clinical challenge. The purpose of this study was to evaluate the use of [ 18 F]2-fluoro-2-deoxy-D-glucose PET/CT (FDG PET/CT with early and delayed imaging) in patients with symptomatic neurofibromas, to revalidate current cut-off values for identification of malignant change within neurofibromas and to examine the relationship between SUV and tumour grade. Methods Patients with symptomatic neurofibromas under- went FDG PET/CT imaging at 90 and 240 min. Semiquan- titative analysis using maximum standardized uptake value (SUVmax) was performed and correlated with histology. Result In 69 patients, 85 lesions were identified for analysis, including 10 atypical neurofibromas and 21 MPNSTs. Sensitivity of FDG PET/CT in diagnosing NF1- associated MPNST was 0.97 (95% CI 0.81–0.99) and the specificity was 0.87 (CI 0.74–0.95). There was a significant difference in SUVmax between early and delayed imaging and in SUVmax between tumours identified as benign and malignant on PET/CT. There was also a significant difference in SUVmax between tumour grades. Conclusion FDG PET/CT is a highly sensitive and specific imaging modality for the diagnosis of MPNST in NF1 patients. We recommend performing early (90 min) and delayed imaging at 4 h for accurate lesion characterization and using a cut-off SUVmax of 3.5 on delayed imaging to achieve maximal sensitivity. Keywords FDG PET . Malignant peripheral nerve sheath tumour . Neurofibromatosis 1 . Plexiform neurofibroma Introduction Neurofibromatosis 1 (NF1) is a common autosomal dominant neurocutaneous disorder with a birth incidence of 1 in 2,500 to 1 in 3,000 [1]. The major diagnostic manifestations include café au lait patches, neurofibromas, skinfold freckling, iris Lisch nodules, optic pathway glioma and distinctive bony dysplasia. The neurofibroma, a benign peripheral nerve sheath tumour, is the most common tumour in NF1 patients and may manifest as focal dermal, cutaneous or subcutaneous growths, intraforaminal spinal nerve root tumours or diffuse plexiform neurofibromas [2]. The complications of NF1 are unpredictable and wide- spread. Neurological problems originate from central nervous system tumours and malformations and as a Eur J Nucl Med Mol Imaging (2009) 36:751–757 DOI 10.1007/s00259-008-1038-0 V. S. Warbey (*) : M. J. O’Doherty Clinical PET Centre, Guy’ s and St Thomas’ NHS Foundation Trust, King’ s College London, London, UK e-mail: vikkiwarbey@doctors.org.uk J. T. Dunn Clinical PET Centre, Division of Imaging Sciences, Guy’ s, King’ s & St Thomas’ School of Medicine, King’ s College London, London, UK R. E. Ferner Department of Neurology, Guy’ s and St Thomas’ Hospitals NHS Foundation Trust, King’ s College London, London, UK E. Calonje Department of Dermatopathology, Guy’ s and St Thomas’ Hospitals NHS Foundation Trust, London, UK