18F-fluorodeoxyglucose positron emission tomography/computed tomography findings of gastric lymphoma: Comparisons with gastric cancer

The role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in numerous malignant tumors, including gastric lymphoma, is well-established. However, there have been few studies with regard to the 18F-FDG PET/CT features of gastric lymphoma. The aim of the present study was to characterize the 18F-FDG PET/CT features of gastric lymphoma, which were compared with those of gastric cancer. Prior to treatment, 18F-FDG PET/CT was performed on 24 patients with gastric lymphoma and 43 patients with gastric cancer. The 18F-FDG PET/CT pattern of gastric wall lesions was classified as one of three types: Type I, diffuse thickening of the gastric wall with increased FDG uptake infiltrating more than one-third of the total stomach; type II, segmental thickening of the gastric wall with elevated FDG uptake involving less than one-third of the total stomach; and type III, local thickening of the gastric wall with focal FDG uptake. The incidence of the involvement of more than one region of the stomach was higher in the patients with gastric lymphoma than in those with gastric cancer. Gastric FDG uptake was demonstrated in 23 of the 24 patients (95.8%) with gastric lymphoma and in 40 of the 43 patients (93.0%) with gastric cancer. Gastric lymphoma predominantly presented with type I and II lesions, whereas gastric cancer mainly presented with type II and III lesions. The maximal thickness was larger and the maximal standard uptake value (SUVmax) was higher in the patients with gastric lymphoma compared with those with gastric cancer. A positive correlation between the maximal thickness and SUVmax was confirmed for the gastric cancer lesions, but not for the gastric lymphoma lesions. There was no difference in the maximal thickness and SUVmax of the gastric wall lesions between the patients without and with extragastric involvement, for gastric lymphoma and gastric cancer. Overall, certain differences exist in the findings between gastric lymphoma and gastric cancer patients on 18F-FDG PET/CT images, which may contribute to the identification of gastric lymphoma.