18F-FDG PET/CT Evaluation of Lymphoma with Renal Involvement: Comparison with Renal Carcinoma

Objective: Lymphoma can arise at any anatomic site, but it is rare to find kidney involvement. The aim of this study was to assess the role of F-18-flourodeoxyglucose (F-18-FDG) positron emission tomography (PET)/computed tomography (CT) in detecting lymphoma with renal involvement. Reports of such use of F-18-FDG PET/CT are limited. Methods: Twelve lymphoma patients with renal involvement and 12 renal carcinoma patients were studied with F-18-FDG PET/CT. Intense F-18-FDG uptake, suggestive of positivity, was measured in mean standardized uptake values (standardized uptake values [SUV] mean). Results: The results of PET/CT were validated by bone marrow, biopsy tissue and/or surgery. F-18-FDG PET/CT detected lymphoma with renal involvement lesions or renal carcinoma lesions in at least one site in the 24 patients. F-18-FDG uptake by the lymphoma lesions was much higher than the F-18-FDG uptake by the renal clear cell carcinomas (SUV mean 6.37 +/- 2.28 vs 2.58 +/- 0.62), and similar to that of renal cell carcinoma and renal collecting duct carcinoma (SUV mean 6.37 +/- 2.28 vs 6.27 +/- 1.15). There were dissimilar morphological changes in the homologous CT. Differing from renal cancer, lymphoma in the spleen, uterus, and bone marrow can easily be diagnosed by F-18-FDG PET/CT. Conclusion: The lesions of lymphoma with renal involvement, and especially those of primary renal lymphoma, are F-18-FDG avid. PET/CT appears to be useful in comparing these lesions with those of renal carcinoma, especially for primary renal lymphoma.