Beyond the lymph nodes: FDG-PET/CT in primary extranodal lymphoma

Extranodal lymphoma can be the primary presentation or secondary to systemic involvement of lymphoma. 2-(fluorine-18) fluoro-2-deoxy-d-glucose positron emission tomography with computer tomography (FDG-PET/CT) is useful in detecting extranodal sites during staging, treatment response assessment or recurrence detection in patients with lymphoma. In this article, we reviewed the imaging features and FDG avidity of primary extranodal lymphoma of various organs and systems on FDG-PET/CT, demonstrating the pearls and pitfalls of FDG-PET/CT in evaluating this disease entity and cross-referencing to other imaging modalities that aid in diagnosis and management.