Inflammatory pseudotumor-like follicular dendritic cell sarcoma of the spleen: A diagnostic challenge with imaging-pathologic correlation.

Epstein-Barr virus (EBV)-associated inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is a rare neoplasm that most commonly arises in the spleen or liver and is frequently misdiagnosed due to nonspecific clinical and imaging features. We report the case of a 46-year-old man presenting with intermittent left upper abdominal discomfort and an incidentally detected splenic mass. Ultrasonography and contrast-enhanced computed tomography demonstrated a heterogeneous lesion with relatively marked arterial-phase enhancement and persistent internal heterogeneity on the venous phase. These findings were indeterminate, and a malignant primary splenic neoplasm could not be excluded; laparoscopic splenectomy was therefore performed. Histopathological examination revealed spindle-to-oval tumor cells within a prominent inflammatory background. Immunohistochemical analysis showed positivity for follicular dendritic cell markers, including CD21 and CD23, and in situ hybridization confirmed Epstein-Barr virus-encoded RNA (EBER) positivity, establishing the diagnosis of IPT-like FDCS. The postoperative course was uneventful, though no follow-up data were available. This case highlights the diagnostic difficulty of splenic IPT-like FDCS, which may mimic other benign and malignant splenic tumors on imaging. Imaging heterogeneity in this case directly reflected the tumor's mixed microscopic composition of fibrotic stroma, inflammatory infiltrate, and viable neoplastic tissue. CT findings alone are insufficient for a definitive diagnosis; however, careful assessment of lesion heterogeneity, enhancement pattern, and the absence of overt extra-splenic disease may help include IPT-like FDCS in the differential diagnosis. Correlation with histopathological findings, follicular dendritic cell marker expression, and EBER in situ hybridization is essential for accurate diagnosis.