Intracholecystic Papillary Neoplasm Mimicking High-Grade Dedifferentiation in a Patient With Neuroendocrine Tumor: The Value of Dual-Tracer PET/CT.
Caner Simsir, Kerem Yılmaz, Saadettin Kılıçkap et al.
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Case in brief
A 50-year-old man with weight loss and fatigue was diagnosed with a grade 2 pancreatic neuroendocrine tumor with liver metastases. For staging, 18F-FDG PET/CT showed high uptake in a gallbladder lesion (SUVmax: 10), whereas the liver metastases were not FDG-avid. 68Ga-DOTATATE PET/CT showed intense somatostatin receptor expression in the pancreatic primary and liver metastases but no uptake in the gallbladder lesion. Although this discordant pattern suggested high-grade dedifferentiation, histopathology after cholecystectomy identified a low-grade intracholecystic papillary neoplasm.
What made this case unusual
The gallbladder lesion produced an FDG-positive/SSTR-negative “flip-flop” pattern suggestive of aggressive NET biology, but proved to be a low-grade premalignant neoplasm rather than dedifferentiated tumor.
Diagnostic / clinical pearl
In a patient with NET, discordant FDG-positive/SSTR-negative uptake may reflect a separate gallbladder lesion, not necessarily high-grade dedifferentiation; correlate imaging with histopathology.