Positron emission tomography (PET) is used for staging and response evaluation in primary gastric lymphoma (PGL). However, the implications of [(18)F]-2-fluoro-2-deoxy-D-glucose ((18)F-FDG) uptake in PGL at first diagnosis have not been reported. The relationship between (18)F-FDG uptake and the expression of facilitative glucose transporters (GLUTs), hexokinase II (HK II), and Ki67, as well as malignant potential in PGL, was assessed in this study. We analyzed 23 patients with PGL [nine with diffuse large B-cell lymphoma (DLBCL); seven with high-grade mucosa-associated lymphoid tissue (MALT) lymphoma; and seven with low-grade MALT lymphoma]. The expression levels of GLUT1, GLUT3, HK II, and Ki67 were evaluated according to the percentage of positive area determined by immunohistochemistry. Standardized uptake values correlated significantly with pathological malignant potentials (low-grade/high-grade MALT lymphoma and DLBCL: p = 0.001-0.002), Ki67 (p < 0.001), and GLUT1 expression (p = 0.02). We determined that (18)F-FDG uptake is related to GLUT1 expression and tumor histological grade as well as Ki67 in PGL.

F-18 FDG PET may be a useful method for evaluating protrusion-type gastric MALT lymphoma. When strong focal or diffuse F-18 FDG uptake is detected in the stomach, endoscopic biopsy should be performed, even if the endoscopic finding is chronic gastritis.

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A 74-year-old woman had dysphagia and underwent esophagogastroduodenoscopy. A giant submucosal tumor was seen from the middle to the lower esophagus. Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG-PET/CT) was performed and F-18 FDG was found to accumulate in the submucosal tumor. The maximum standardized uptake value of the early phase was 4.93 and that of the delayed phase was 6.48. Gastrointestinal stromal tumor (GIST) was confirmed by both fine needle aspiration under endoscopic ultrasound and postoperative histopathologic findings. We stained the postoperative histopathologic specimen to investigate glucose transporter (GLUT) expression using immunohistochemistry, which revealed that GLUT-1 had a weak expression on membranes and GLUT-4 had a strong expression on membranes or in cytoplasm. GLUT-3 had no expression on membranes or in cytoplasm. Esophageal GIST is rare and the relationship between GLUT expression and F-18 FDG accumulation in GIST is probably rare.

Concentric contour and stricture wall thicknesses of <3.0 mm may help distinguish between SC-AIP and IEC.