This case illustrates an incidental gallbladder adenocarcinoma that has been missed on imaging and during the cholecystectomy, only picked later on the histopathology assessment and review of the images. The clinical presentation with acute symptoms and picture mimicking acute cholecystitis, together with a more discrete and not mass-like tumor appearance, lead it to be missed. 

As such in this case, gallbladder carcinomas predominantly affect older persons with long-standing cholelithiasis, and as such is most common in elderly women. On imaging, the gallbladder is not abnormally distended and narrows with a funnelling appearance at its infundibulum, where there is focal restricted diffusion of its wall. This type of tumor presentation is the most frequently missed and mistaken for cholecystitis.