PET-Negative Gastrointestinal Stromal Tumors

Area of Science:

• Oncology
• Nuclear Medicine
• Radiology

Background:

• Gastrointestinal stromal tumors (GISTs) represent the most frequent mesenchymal malignancy within the gastrointestinal tract.
• Positron Emission Tomography/Computed Tomography (PET/CT) is a standard imaging modality for GIST diagnosis and therapy response assessment.

Observation:

• GISTs characteristically exhibit intense uptake of (18)F-fluorodeoxyglucose (FDG), a common radiotracer used in PET scans.
• This report details two distinct cases of GIST that presented with unexpectedly low or negative FDG uptake on PET/CT imaging.

Findings:

• The presented cases highlight that diminished or absent FDG avidity can occur in GISTs.
• This finding challenges the typical assumption of high FDG uptake in all GISTs.

Implications:

• The diagnostic criteria for GIST should consider the possibility of low/negative FDG uptake.
• FDG-PET/CT results should be interpreted cautiously in the context of suspected GIST, especially when combined with other clinical and pathological data.
• Further research may elucidate the specific characteristics or subtypes of GIST that exhibit reduced FDG uptake.