Mass-forming pancreatitis (MFP) resembles pancreatic adenocarcinoma on CT scan, and differentiating one from the other can be challenging. FDG PET/CT has been found to be better in distinguishing MFP from pancreatic adenocarcinoma by virtue of lower tracer uptake in the inflammatory lesion [5, 6]. However, certain cases of MFP can show high FDG avidity due to the inflammatory process and can simulate malignancy (Fig. 5.4).

Gall bladder wall thickening can be because of benign causes like inflammation and adenomyosis or due to malignancy. FDG PET can be falsely positive in cases of cholecystitis, and differentiation from malignancy can be difficult [7, 8]. Mass-like or protuberant lesions are more likely to be due to malignancy. Diffuse and uniform FDG avid wall thickening is usually due to inflammation (Fig. 5.5), though imaging features can overlap.

Significant proportion of gall bladder cancers are diagnosed incidentally from the surgical specimen after elective cholecystectomy is performed for symptomatic calculus disease. Staging PET/CT studies then performed often show FDG uptake in the operated bed of the gall bladder fossa which is due to postoperative inflammation associated with normal healing [2, 9]. This false-positive FDG uptake can persist for several weeks after surgery and mimic disease leading to futile surgical explorations to remove residual disease (Fig. 5.6).