Beyond lymph nodes: 18F-FDG PET/CT in detection of unusual sites of extranodal lymphoma

Abstract

Background: The purpose of this study was to compare between contrast-enhanced computer tomography (CE CT) and 18F-FDG PET/CT in the detection of extranodal involvement in lymphoma and to correlate between SUVmax of the extranodal lesion and the hottest LN. One hundred patients with pathologically proven lymphoma underwent whole body 18F-FDG PET/CT and CECT scans. Images were compared regarding the ability of detection of extranodal lymphomatous sites. Kappa agreement was applied to find the degree of agreement between both modalities. Pearson’s correlation was used for correlating SUVmax of the extranodal lesions and hottest LN. The degree of FDG uptake was correlated with histopathological type. Results: There was a poor agreement between PET/CT and CECT in the detection of extranodal sites (k = 0.32). There was a significant positive moderate correlation between SUVmax of the extranodal lesions and hottest LN (r = 0.45). PET/CT study resulted in up staging of 10% and down staging of 5% of cases. Conclusion: In lymphoma staging, FDG PET/CT enables more detection of extranodal involved sites that show normal morphology at CECT. It differentiates lymphomatous infiltration from benign causes of increased FDG uptake with subsequent proper disease staging.