Case Report: Primary pulmonary lymphoma with CT negative and PET high metabolism combined with hemophagocytic syndrome

Background Primary pulmonary diffuse large B-cell lymphoma (DLBCL) is usually accompanied by imaging visible lesions. Cases with normal CT morphology and high PET metabolism are extremely rare, especially when combined with hemophagocytic syndrome (HLH). Case We present the case of a 50-year-old man who presented with fever of unknown origin (FUO) in March 2023. Chest CT showed no abnormalities, while positron emission tomography/computed tomography (PET/CT) showed diffuse hypermetabolism in both lungs (SUVmax 5.1) and slightly increased bone marrow uptake (SUVmax 3.1). Laboratory tests showed a significant increase in ferritin (1132.37 ng / mL) and C-reactive protein (CRP) (115.38 mg/L). Bone marrow smears showed hemophagocytosis. A lung biopsy guided by PET metabolic focus confirmed DLBCL (germinal center type). Complete metabolic remission was achieved after four cycles of R-CEOP chemotherapy. Conclusion Primary pulmonary lymphoma (PPL) should be considered in patients with diffuse increased 18F-FDG uptake in both lungs and accompanied by hemophagocytic syndrome when they do not meet the imaging findings of common lung diseases, and the site of increased uptake should be selected for pathological biopsy.