CT and MRI characteristics of inflammatory pseudotumor-like follicular dendritic cell sarcoma of the spleen: a report of 11 patients with pathological correlation.

Objective: This study aimed to outline the computed tomography (CT) and magnetic resonance imaging (MRI) characteristics of inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) in the spleen and to link these imaging features with histopathological findings.

Materials and methods: A retrospective analysis was conducted on 11 patients (3 males, 8 females; mean age, 63.3 ± 9.66 years; age range, 44-76 years; median age, 62 years) with histopathologically confirmed inflammatory pseudotumor-like follicular dendritic cell sarcoma of the spleen (IPT-like FDCS). The study encompassed a comprehensive review of initial clinical manifestations, macroscopic pathological alterations, along with histopathological and corresponding immunohistochemical findings. CT (n = 10) and MRI (n = 8) characteristics were meticulously assessed by two experienced radiologists, who evaluated parameters including lesion number, size, shape, margin definition, capsular integrity, attenuation, signal intensity, presence of hemosiderin deposition, and patterns of contrast enhancement.

Results: In this study, all eleven patients (11/11; 100%) presented with solitary inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS). The majority of these cases were incidentally detected during routine physical examinations, while one case was revealed through abdominal CT following a decline in platelet count post-radiation and chemotherapy for prostate cancer. The splenic lesions were predominantly oval in shape (10/11; 91%), with a single case exhibiting a lobulated appearance (1/11; 9%). The largest lesion diameter was 18 cm, with diameters ranging from 3.3 to 18 cm, averaged 6.5 cm, and a median diameter of 5.0 cm. On plain CT images, the lesions were primarily observed as hypodense with poorly defined margins. On contrast-enhanced CT, all lesions (10/10; 100%) promptly became sharply demarcated in the arterial phase, encircled by a perceptible, relatively hypodense capsule-like rim. On T2-weighted MRI, all lesions (8/8; 100%) displayed a characteristic rim-like low-intensity capsular margin. These low-signal/density capsular margins were pathologically confirmed to be capsules containing fibrous components.

Conclusions: IPT-like FDCS is very rare but has characteristic imaging features that correlate with its pathology.