FDG PET/CT of Extranodal Involvement in Non-Hodgkin Lymphoma and Hodgkin Disease

Abstract

The term extranodal disease refers to lymphomatous infiltration of anatomic sites other than the lymph nodes. Almost any organ can be affected by lymphoma, with the most common extranodal sites of involvement being the stomach, spleen, Waldeyer ring, central nervous system, lung, bone, and skin. The prevalence of extranodal involvement in non-Hodgkin lymphoma and Hodgkin disease has increased in the past decade. The imaging characteristics of extranodal involvement can be subtle or absent at conventional computed tomography (CT). Imaging of tumor metabolism with 2-[fluorine-18]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) has facilitated the identification of affected extranodal sites, even when CT has demonstrated no lesions. More recently, hybrid PET/CT has become the standard imaging modality for initial staging, follow-up, and treatment response assessment in patients with lymphoma and has proved superior to CT in these settings. Certain PET/CT patterns are suggestive of extranodal disease and can help differentiate tumor from normal physiologic FDG activity, particularly in the mucosal tissues, bone marrow, and organs of the gastrointestinal tract. Familiarity with the different extranodal manifestations in various locations is critical for correct image interpretation. In addition, a knowledge of the differences in FDG avidity among the histologic subtypes of lymphoma, appropriate timing of scanning after therapeutic interventions, and use of techniques to prevent brown fat uptake are essential for providing the oncologist with accurate information.

Extensive Extranodal Involvement of Rare Sites in Non Hodgkin’s Lymphoma Detected on 18F- FDG PET-CT: A Case Report

“…The most common histological type is DLBCL. Inguinal and retroperitoneal lymph nodal spread can also be seen in some patients [2]. In our case, there was abnormally increased asymmetric radiotracer uptake in the enlarged left testis.…”

“…Findings were suggestive of lymphomatous involvement of above mentioned sites As 18 F-FDG is excreted by the kidneys, it can lead to false positive and false negative interpretations on PET-CT. Renal involvement in NHL is seen as multiple focal areas of increased 18 F-FDG uptake mostly in renal cortices that may be unilateral or less commonly, bilateral. There may or may not be corresponding lesions in non diagnostic CT scans [2]. In the present case, multiple focal areas of increased radiotracer uptake were noted in bilateral renal cortices.…”

“…The stomach is the most commonly affected followed by small bowel, large bowel, and esophagus [2]. In the small bowel, NHL usually occurs due to the direct extension of disease from the involved mesenteric lymph nodes and the distal ileum is most frequently affected site [17].…”

“…Malignancies of lymphoid cells may present as leukemia (i.e., primary involvement of bone marrow and blood), or as lymphoma (i.e., solid tumors of the immune system) [1]. The role of 18 F-fluorodeoxyglucose positron emission tomography ( 18 F-FDG PET) and PET-CT (positron emission tomography-computed tomography) has been extensively evaluated in the management of Hodgkin's disease (HD) and non Hodgkin's lymphoma (NHL) [2][3][4][5][6][7]. PET-CT has shown significant improvement in staging and restaging when compared to conventional imaging modalities such as contrast-enhanced computed tomography (CECT) [4][5][6][7].…”

“…PET-CT has shown significant improvement in staging and restaging when compared to conventional imaging modalities such as contrast-enhanced computed tomography (CECT) [4][5][6][7]. The role of 18 F-FDG PET-CT in detection, staging and restaging of patients with extranodal involvement in NHL has also been reported in the literature [2,3]. Multiple isolated cases with extranodal involvement of NHL, detected on PET-CT, have been previously reported [8][9][10][11].…”