Background: Malignant peripheral nerve sheath tumours (MPNSTs) are difficult to detect in neurofibromatosis 1 (NF1) individuals. The purpose was to evaluate [18F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) and PET computed tomography (CT) as a diagnostic tool for MPNST in NF1 patients with symptomatic plexiform neurofibromas and to verify the diagnosis by pathology and clinical follow-up. Patients and methods: NF1 individuals with symptomatic plexiform neurofibromas underwent clinical evaluation and magnetic resonance imaging. Qualitative FDG PET and PET CT associated with semi-quantitative maximum standard uptake value (SUVmax) assessed possible malignant change. Excision/biopsy verified the diagnosis when possible and clinical follow-up was undertaken in all patients. Results: In all, 116 lesions were detected in 105 patients aged 5–71 years, including 80 plexiform neurofibromas, five atypical neurofibromas, 29 MPNST and two other cancers. Biopsy confirmed the findings in 59 tumours and no MPNST was diagnosed on clinical follow-up of 23 lesions diagnosed as benign on FDG PET and PET CT. FDG PET and PET CT diagnosed NF1-associated tumours with a sensitivity of 0.89 [95% confidence interval (CI) 0.76–0.96] and a specificity of 0.95 (CI 0.88–0.98), but the SUVmax level did not predict tumour grade. Conclusion: FDG PET and PET CT is a sensitive and specific diagnostic tool for NF1-associated MPNST. Other PET tracers will be required to solve the problem of predicting tumour grade. |