Fluorine-18 Fluorodeoxyglucose PET/CT Patterns of Extranodal Involvement in Patients with Non-Hodgkin Lymphoma and Hodgkin's Disease

Lymphoma may originate in extranodal sites. ENL may also be secondary to and accompany nodal disease. ENL is probably more common than previously thought, with an incidence of approximately 25% in the overall population of patients with lymphoma, which may be even higher in some specific subtypes, such as MALT. ¹⁸F-FDG imaging has an essential role in the staging of lymphoma, in monitoring the response to therapy, and in detection of recurrence. The introduction of ¹⁸F-FDG PET/CT hybrid imaging allows for accurate localization of disease and may be specifically beneficial for the detection of unexpected extranodal sites of disease or exclusion of disease in the presence of nonspecific extranodal CT findings. Accurate staging and localization often dictate the appropriate treatment strategy in patients with lymphoma. Therefore, at any stage in the course of the disease, the potential presence of extranodal disease should be considered when interpreting ¹⁸F-FDG PET/CT studies in patients with NHL and HD.