Objective  To enhance comprehension of undifferentiated embryonal sarcoma of the liver (UESL) in children by analyzing ultrasound, CT, and MRI imaging features.

  Methods  A retrospective analysis was conducted on 11 cases of UESL in children, confirmed through surgery and pathology, at the Children's Hospital, Affiliated Capital Institute of Pediatrics from December 2009 to December 2021. We analyzed the ultrasound, CT, and MRI imaging features of all patients and summarized their characteristics.

  Results  All 11 cases presented with solitary hepatic masses ranging from 11.5 to 19.8 cm in diameter. Imaging manifestations of UESL correlated with component proportion and distribution within the masses. Lesions displayed clear boundaries in all cases. CT scans revealed mixed low density in 11 cases, with irregular floc soft tissue density shadows observed at the edge of cystic density areas or around partitions in a few cases. Ultrasound images of all six cases showed solid space-occupying masses, with varying sizes of anechoic regions within the solid mass. MRI T1WI showed mixed low intensity signal in three cases and strip/large high intensity signal areas in the lesion. T2WI revealed mixed high intensity signal and strip low intensity signal areas in 3 lesions. In the arterial phase, lesions displayed slightly to moderately heterogeneous strip/patch enhancement, primarily marginal enhancement in nine cases and thickened, tortuous arterial shadows in eight cases. In the delayed phase, lesions showed continuous uneven enhancement, with enhancement at the edge and peripheral-to-central filling observed in eight cases. Additionally, the enhancement range continuously increased in eight cases, with the false capsule sign identified in eight cases in the delayed stage.

  Conclusions  Imaging features of UESL in children exhibit distinct characteristics. Understanding these features, in conjunction with clinical findings, may aid in early diagnosis.