Intense FDG Uptake in an α-SMA–positive Epstein–Barr Virus–associated Inflammatory Follicular Dendritic Cell Sarcoma of the Spleen

We report a case of Epstein–Barr virus–positive inflammatory follicular dendritic cell sarcoma (EBV+ IFDCS) of the spleen demonstrating myofibroblastic differentiation with α-smooth muscle actin (α-SMA) expression. A 67-year-old woman was incidentally found to have a 45-mm splenic mass during postoperative surveillance for lung cancer. CT and MRI revealed a well-circumscribed lesion with a fibrous capsule and heterogeneous necrotic components, showing gradual enhancement. FDG-PET/CT demonstrated intense focal uptake (SUVmax=8.40) without additional hypermetabolic lesions. Histopathologic examination showed EBV positivity and CD23 expression with prominent inflammatory infiltrates. Notably, α-SMA expression suggested myofibroblastic differentiation. This case highlights the imaging features of EBV+ IFDCS and suggests a possible association between myofibroblastic differentiation and radiologic characteristics.