Characterization of CT and MRI findings in sclerosing angiomatoid nodular transformation of the spleen: novel discovery of peritumoral vascular signs.

Background: Sclerosing angiomatoid nodular transformation (SANT) is a rare benign vascular lesion of the spleen. Previous studies have described some imaging characteristics, such as centrifugal or centripetal enhancement patterns. However, comprehensive descriptions of imaging features, especially peritumoral vascular changes, remain limited. This study aimed to characterize the imaging features of SANT of the spleen, with a focus on identifying peritumoral vascular changes. Methods: A retrospective analysis was conducted on 57 consecutive cases of SANT, including clinical, pathological, and imaging data. Imaging modalities included computed tomography (CT) scans in 41 individuals and magnetic resonance imaging (MRI) scans in 34 individuals. Results: All 57 cases exhibited well-circumscribed lesion margins. Solitary lesions were observed in 54 cases, while 3 cases exhibited multiple lesions. Peritumoral vascularity was observed in 43 cases, of which 7 demonstrated peritumoral vascularity with a ball-holding appearance. On non-contrast CT, the lesions displayed low-density signals, with calcifications observed in 9 cases. The enhancement patterns were categorized as follows: spoke-wheel centripetal enhancement (13 cases), nodular centripetal enhancement (12 cases), and progressive centripetal enhancement (16 cases). On MRI T2-weighted imaging (T2WI), 23 lesions exhibited low signal intensity, 10 showed mixed high and low signal intensity, and 1 displayed high signal intensity. Diffusion-weighted imaging (DWI) findings revealed heterogeneously mixed high and low signal intensities in eight cases, heterogeneous low signal intensity in 25 cases, and homogeneous high signal intensity in 1 case. The enhancement patterns of the lesions were categorized as follows: spoke-wheel centripetal enhancement pattern (18 cases), nodular centripetal enhancement pattern (12 cases), and progressive centripetal enhancement pattern (4 cases). Conclusions: The distinct imaging characteristics of splenic SANT, including newly identified markers, such as the presence of peritumoral vascularity and the ball-holding appearance of peritumoral vessels, provide valuable insights for accurate diagnosis and differentiation of the splenic SANT from other splenic lesions.