Article Text
Abstract
OBJECTIVES The ability of 18fluorodeoxyglucose positron emission tomography (18FDG PET) to detect malignant change in plexiform neurofibromas from patients with neurofibromatosis 1 (NF1) was evaluated.
METHODS Eighteen NF1 patients who presented with pain, increase in size, or neurological deficit associated with a plexiform neurofibroma were assessed. Magnetic resonance imaging determined the site and extent of the lesion. Qualitative18FDG PET was performed and the standard uptake value (SUV) measured the regional glucose metabolism. Histological confirmation of the diagnosis was obtained in 10 patients.
RESULTS Twenty three plexiform neurofibromas were detected in 18 patients. Seven malignant peripheral nerve sheath tumours, four high grade and three low grade tumours, occurred in five patients. In one patient the clinical and radiological characteristics of the tumour suggested malignancy, but histology was inconclusive. Fifteen benign plexiform neurofibromas were identified in 12 patients and these findings were confirmed histologically in five lesions from four patients. Ten plexiform neurofibromas occurring in eight patients were considered benign on18FDG PET and the patients did not undergo surgery. They remained stable or their symptoms improved on clinical follow up (median 9 months). The results of qualitative 18FDG PET were interpreted as indicating that 13 plexiform neurofibromas were benign and 10 were malignant. No malignant tumours were classified as benign, but two benign tumours were reported as malignant. The SUV was calculated for 20 tumours and was significantly higher in five malignant tumours 5.4 (SD 2.4), than in 15 benign tumours 1.54 (SD 0.7), p=0.002. There was an overlap between benign and malignant tumours in the SUV range 2.7–3.3.
CONCLUSIONS 18FDG PET is helpful in determining malignant change in plexiform neurofibromas in NF1. Increased separation between benign and malignant lesions could be obtained by calculating the SUV at about 200 minutes after injection of 18FDG, when the peak activity concentration is obtained in malignant tumours.
- neurofibromatosis 1
- plexiform neurofibroma
- malignant peripheral nerve
- sheath tumour
- 18FDG positron emission tomography