Description
A middle-aged patient with known neurofibromatosis type 1 (NF1) presented with an increase in the size and number of cutaneous lesions. The lesions were further evaluated with positron emission tomography (PET)/CT that showed diffuse hypermetabolic neurofibromas of the neck, thorax, proximal lower extremities (figure 1) and a fluorodeoxyglucose (FDG)-avid lesion in the left lower abdominal quadrant. Biopsy of the FDG-avid lesions on the left shoulder and right thigh were histologically consistent with neurofibromas. A composite PET/CT fused image (figure 2) demonstrated a FDG-avid lesion in the small bowel, and the corresponding CT images showed a 3.5 cm contrast-enhancing mass arising from the jejunum (figure 3). Subsequent biopsy, surgery and pathology found a low-risk 3.6 cm gastrointestinal stromal tumour (GIST) with two tiny GISTs in close proximity beyond PET and CT resolution.
Figure 1.
Coronal positron emission tomography/CT image demonstrating diffused hypermetabolic lesions in the neck, thorax and proximal lower extremities consistent with neurofibromas. A further fluorodeoxyglucose-avid lesion (black arrow) is identified in the left lower abdominal quadrant.
Figure 2.
An axial composite positron emission tomography/CT fused image demonstrating a suspicious fluorodeoxyglucose-avid lesion arising from the small bowel (white arrow).
Figure 3.
Axial CT image showing a contrast-enhancing mass arising from the jejunum (white arrow).
There is a known association between NF1 and GISTs, with GISTs developing in 5–30% of patients with NF1.1 The role of PET/CT in GISTs is not yet well established, but is useful in assessing tumour response to tyrosine kinase inhibitors therapy.2 The most frequent tumours seen in NF1 are neurofibromas. Of concern, these may transform from benign plexiform neurofibroma (PNF) into malignant peripheral nerve sheath tumours (MPNST). FDG-PET and PET/CT have demonstrated their clinical utility in discriminating between benign PNF and MPNST based on maximal standard uptake values.3
Learning points.
There is a need for close tumour surveillance in the neurofibromatosis type 1 (NF1) population.
Patients with NF1 are at increased risk of several malignancies, including gastrointestinal stromal tumour (GIST) and malignant peripheral nerve sheath tumours.
The incidental finding of GIST demonstrating the clinical utility of positron emission tomography/CT as a diagnostic tool in clinical oncology.
Footnotes
Competing interests: None declared.
Patient consent: Obtained.
Provenance and peer review: Not commissioned; externally peer reviewed.
References
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