18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) for staging and follow-up of marginal zone B-cell lymphoma

Objective: According to recent reports, nodal marginal zone lymphoma (MZL) appears to be a distinctive lymphoma entity rather than a more advanced stage of extranodal MZL of mucosa-associated lymphoid tissue (MALT). We have therefore retrospectively evaluated all patients diagnosed with nodal or extranodal MZL who have been referred to our unit for imaging using F-18-fluorocleoxyglucose positron emission tomography (F-18-FDG-PET). Patients and Methods: A total of 21 patients with a diagnosis of MZL upon referral for imaging with 18F-FDG-PET were identified. Histological reassessment of biopsy specimens confirmed the diagnosis of extranodal MZL of MALT in 14 patients, while a diagnosis of nodal MZL was verified in 6 patients. Lymphoma cell proliferation was assessed immunohistochemically using a Ki-67 antibody. Whole-body 18F-FDG-PET scans were performed on a GE advanced PET scanner 40 min after intravenous injection of 300-380 MBq F-18-FDG. Results: None of the patients with extranodal MZL showed focal tracer uptake within verified tumor sites. In contrast, 5 of the 6 patients with nodal MZL showed significant FDG uptake within the affected lymph nodes. These results did not simply reflect the different growth fractions of the two lymphoma entities since the proliferation indices of the two groups did not differ significantly. Conclusion: 18F-FDG-PET visualizes nodal MZL in a high proportion of patients whereas FDG uptake is undetectable in extranodal MZL. Although limited by the small number of patients, this study suggests that imaging with F-18-FDG-PET might play a potential role in the diagnostic workup of patients with nodal MZL involvement.