Imaging features of inflammatory pseudotumor-like follicular dendritic cell sarcoma of the spleen.

Background: Inflammatory pseudotumor (IPT)-like follicular dendritic cell sarcoma (FDCS) is an extremely rare malignant neoplasm.

Methods: Retrospective analysis of imaging features of splenic IPT-like FDCS, including ultrasonography, computed tomography (CT), and magnetic resonance (MR) and contrast-enhanced imaging were performed.

Results: When the masses were small, the ultrasound images showed homogeneous hypoechoic signals, clear boundaries, and complete capsules. Abdominal plain CT scans showed equal density (easy to miss diagnosis), unclear boundaries, and no capsules. Magnetic resonance images (MRI) showed slightly shorter T1, slightly shorter T2, and clear boundaries. When the masses were large, the ultrasound images still showed clear boundaries and complete capsules, but the echoes of the masses were not uniform, and some of the masses showed dendritic hyperechoic centers. Abdominal plain CT scans showed irregular low densities in the center (unclear boundaries) and equal densities in the periphery. MRI showed short T1 and T2, but the central signals were mixed. When the mass was accompanied by extensive necrosis, abdominal plain CT scan showed mostly cystic lesions and slight calcifications in low density lesions. Contrast-enhanced CT showed only moderate enhancement in peripheral and septal areas. MRI showed that T1 and T2 were mainly mixed signals. Contrast-enhanced MR showed moderate enhancement of peripheral areas and septum.

Conclusions: This is the first report to describe the IPT manifestations of the spleen (ultrasonography, CT, and MR). The diagnosis of IPT can be made by combining three imaging features.