Aim. To systematically review the role of positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose (FDG) in patients with neurofibromatosis type 1 (NF1). Methods. A comprehensive literature search of published studies regarding FDG-PET and PET/CT in patients with NF1 was performed. No beginning date limit and language restriction were used; the search was updated until December 2011. Only those studies or subsets in studies including whole-body FDG-PET or PET/CT scans performed in patients with NF1 were included. Results. We identified 12 studies including 352 NF1 patients. Qualitative evaluation was performed in about half of the studies and semiquantitative analysis, mainly based on different values of SUV cutoff, in the others. Most of the studies evaluated the role of FDG-PET for differentiating benign from malignant peripheral nerve sheath tumors (MPNSTs). Malignant lesions were detected with a sensitivity ranging between 100% and 89%, but with lower specificity, ranging between 100% and 72%. Moreover, FDG-PET seems to be an important imaging modality for predicting the progression to MPNST and the outcome in patients with MPNST. Two studies evaluated the role of FDG-PET in pediatric patients with NF1. Conclusions. FDG-PET and PET/CT are useful methods to identify malignant change in neurogenic tumors in NF1 and to discriminate malignant from benign neurogenic lesions. 1. Introduction Neurofibromatosis type 1 (NF1) is an autosomal dominant disease with an incidence of 1 in 2,500 to 1 in 3,000 subjects. Neurofibroma, a benign peripheral nerve sheath tumor, is the most common tumor in NF1 patients and may manifest as focal nodular, cutaneous or subcutaneous lesion, intraforaminal spinal nerve root tumor, or plexiform neurofibroma (PNF). Patients with NF1 have an increased risk of developing malignant peripheral nerve sheath tumors (MPNSTs) with a life-time risk of 8–12% [1–6]. MPNSTs usually arise from preexisting benign PNF, metastasize widely, and frequently have a poor prognosis. Therefore, differentiating between benign and malignant tumors in patients with NF1 has important prognostic and therapeutic implications, but can be difficult, especially in individuals who have multiple benign tumors. Optimal management is dependent on early and accurate histological grading and staging of the disease, but MPNSTs are often difficult to detect and may metastasize to many different sites. Pain, rapid increase in size of a neurofibroma, and the development of neurological deficit are clinical indicators of malignancy, but may also be features
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