Patterns of FDG uptake in pancreatic non-Hodgkin's lymphoma lesions.

PURPOSE: The aim of this study was to evaluate the pattern of FDG uptake in pancreatic non-Hodgkin's lymphoma (NHL) lesions. METHODS: The study included 9 consecutive patients with newly diagnosed NHL with pancreatic involvement who underwent an F-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) scan. The location, size, maximal standardized uptake value (SUVmax), and FDG uptake patterns of the pancreatic lesions were reviewed. RESULTS: Four different patterns of FDG uptake could be distinguished in the affected pancreas corresponding to different types of lymphoma lesions. These included focal FDG uptake by distinct solitary lesions (5 patients), multiple foci of FDG uptake corresponding to separate lymphoma lesions (1 patient), segmental FDG uptake caused by lymphoma infiltration limited to a pancreatic segment (1 patient), and diffuse FDG uptake related to diffuse lymphomatous infiltration of the entire pancreas (2 patients). All types of lesions showed increased metabolic activity with maximal standardized uptake values (SUVmax) ranging from 7.4 to 26.5. On CT images, the segmental and diffuse patterns of FDG uptake correlated to segmental and diffuse pancreatic enlargement accordingly. All lesions showed isodensity or slight hypodensity in relation to pancreatic tissue. The pancreatic head was the most frequent site of involvement (8/9). Mildly dilated pancreatic duct was noted only in 2 patients. CONCLUSIONS: The described patterns of FDG uptake and correlative CT findings may be helpful for a better characterization of NHL involving the pancreas and for differential diagnosis with other lesions, including pancreatic adenocarcinomas.