F-FDG PET/CT Correctly Differentiates Idiopathic Pericarditis from Recurrent Lymphoma in a Patient with Primary Mediastinal Lymphoma.

A man in his 30s awaiting end-of-treatment F-fluorodeoxyglucose positron emission tomography/CT (F-FDG PET/CT) for primary mediastinal B-cell lymphoma developed chest pain and pericardial effusion. His interim F-FDG PET/CT showed complete metabolic responses. His blood test revealed elevated levels of inflammatory markers, including C-reactive protein of 204.1 mg/L and erythrocyte sedimentation rate of 106 mm/h. His pericardial biopsy revealed organizing fibrinous pericarditis with hemosiderin pigment deposition and no evidence of malignancy or granuloma. The F-FDG PET/CT performed during this episode of illness revealed a mild degree of F-FDG uptake along the pericardial lining [maximum standardized uptake value (SUV) =6.76] compared with the blood pool activity (SUV =3.17), which favors pericarditis over relapsed lymphoma. His symptoms subsided 2 weeks after treatment with an non-steroidal anti-inflammatory drug, and he had no sign of relapsed lymphoma on subsequent follow-ups.