PET-CT Imaging of Extranodal Involvement In Non Hodgkin Lymphoma

Abstract

Background Lymphoid neoplasms are broadly divided into Hodgkin disease (HD) and non-Hodgkin’s lymphoma (NHL). Non-Hodgkin lymphoma accounts for about 5% of all cases of cancer with greater predilection to disseminate to extra-nodal sites. Extranodal lymphoma describes that there is neoplastic proliferation at sites other than the expected native lymph nodes or lymphoid tissue. Lymphomas that initially appear to have the bulk of the disease at extranodal sites are described as primary extranodal lymphoma and categorized as Stage I or II. In secondary extranodal lymphoma, there is secondary involvement of the extranodal sites from primary nodal disease, which is categorized as Stage III or IV. Aim and Objectives To assess the added value of hybrid Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in the evaluation of extranodal involvement in patients with non-Hodgkin lymphoma in comparison to contrast-enhanced CT (CECT). Patients and Methods All patients had Non-Hodgkin lymphoma, proved by histopathological and immunophenotyping examinations. They underwent CECT and F-18 FDG PET–CT studies. Results This study included 76 patients with pathologically confirmed lymphoma who underwent PET/CT study. The patients' ages ranged between 20 and 78 years old (mean age 51 ± 14.7 years). This study included 51 males and 21 females. Diffuse large B-cell lymphoma subtype had the highest prevalence 53% (40/76), whereas mucosa-associated lymphoid tissue lymphoma was the least prevalent 4%. The Spleen was the most common site as it was involved in 20 patients followed by bone and bone marrow 15 patients, lung 13, Liver 9, Nasopharynx 4, Muscular and Cutaneous Nodules 4 patients each, CNS, Adrenal, Renal and Pleural Affection 3 patients each, Tonsillar, stomach, Pancreas and Prostate 2 patients each, and finally only one patient had salivary gland, thyroid, breast, and testicular involvement. The overall sensitivity, specificity, PPV, NPV, and accuracy of PET/CT and CECT are 97%, 20%, 94.5%, 33.3%, 91, 6 % and 87.3%, 60 %, 93.9%, 10% and 87.5%, respectively. Conclusion Combined PET/CT using 18F-FDG is the best oncologic imaging modality at present time with indispensable role and valuable application in monitoring and management of the extranodal lymphoma. It can detect metabolically active lesions without CT structural changes and identify a viable tumor in normal size lymph nodes. PET/CT is more effective than CECT in evaluating extranodal Lymphomatous infiltration, especially in spleen, bone, and bone marrow.