18FDG-PET/CT versus contrast enhanced CT in detection of extra nodal involvement in patients with lymphoma Alnouby. A1, Nasr. I2, Ali. I3, Rezk. M4 1Nuclear Medicine Unit, International Medical Center, 2Oncology and Nuclear Medicine Department, Faculty of Medicine , Zagazig University; 3Radiology Department, Faculty of Medicine , Zagazig University,4Radiology Department, National Cancer Institute, Cairo University. Indian Journal of Nuclear Medicine | Volume 33 | Issue 3 | July‑September 2018 Abstract Aim and Objectives: The aim of this study is 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 lymphoma in comparison to contrast‑enhanced CT (CECT). Patients and Methods: All patients had lymphoma, proved by histopathological and immunophenotyping examinations. They underwent CECT and F-18 FDG PET–CT studies. Both CECT and PET/CT studies were done within 30 days. Results: The study included 144 patients 92 (63.9%) males and 52 (36.1%) females with mean age 49.3 years (range 18–80 years). A total of 102 (70.8%) patients had non‑Hodgkin lymphoma and 42 patients (18.1%) had Hodgkin disease, diffuse large B‑cell lymphoma subtype had the highest prevalence 52.8% (76/144), whereas lymphocytic predominance was the least prevalent 1.4% (2/144) followed by mucosa‑associated lymphoid tissue lymphoma 2.8% (4/144) and small lymphocytic type 4.2% (6/144), mixed cellularity (MC), T‑cell, and follicular type were equally distributed 6.9% (10/144 each). The lung was the most common site as it was involved in 34 patients followed by bone and bone marrow 32 patients, spleen 18, liver 16, nasopharynx 8, stomach 6, cutaneous and subcutaneous tissue 6, peritoneum, cecum, small intestine, brain, and intramuscular four patients each. However, the parotid and pancreas were the least common sites two patients each. The overall sensitivity, specificity PPV, NPV, and accuracy of PET/CT and CECT are 97%, 20% 94.2%, 33.3%, 91.7% and 89.6%, 60%, 96.8%, 30% and 87.5%, respectively. Conclusion: F-18 FDG‑PET/CT can accurately monitor the extranodal lymphoma, it can detect metabolically‑active lesions without CT structural changes and identify viable tumor in normal size lymph nodes. FDG‑PET/CT is more effective than CECT in evaluating extra nodal lymphomatous infiltration, especially in the spleen, bone, and bone marrow. Keywords: Diffuse large B‑cell lymphoma and 18‑fluorodeoxyglucose positron emission tomography/