Undifferentiated embryonal sarcoma of the liver presenting as a complex mixed solid-cystic hepatic lesion in a young adult: A case report.

Undifferentiated embryonal sarcoma of the liver (UESL) is a rare and aggressive primary hepatic mesenchymal malignancy, predominantly affecting children aged 6-10 years but occasionally arising in young adults. Diagnosis is clinically challenging owing to paradoxical and nonspecific imaging features that vary across modalities, contributing to misdiagnosis rates of up to 23.5%. We report a 23-year-old woman who presented with a 6-week history of right upper quadrant pain, normal liver function tests, and unremarkable tumor markers. Abdominal ultrasound demonstrated a solid-appearing, heterogeneously echoic hepatic mass, while computed tomography and magnetic resonance imaging revealed a predominantly cystic lesion with enhancing internal septations, serpiginous peripheral vessels, intertumoral hemorrhage, fluid-fluid levels, and restricted diffusion-a characteristic cross-modal discordance typical of UESL. Following multidisciplinary team review, the patient underwent right hemi hepatectomy without preoperative biopsy. Histopathology confirmed UESL with classic spindle and stellate cells in a fibro myxoid background, diastase-resistant periodic acid-Schiff-positive eosinophilic globules, and an immunohistochemical profile consistent with primitive mesenchymal origin. Adjuvant chemotherapy with ifosfamide and epirubicin was administered, and 12-month surveillance imaging demonstrated no recurrence. This case illustrates that cross-modal imaging discordance in a young adult with a large complex hepatic lesion and normal tumor markers should raise suspicion for UESL, and supports upfront surgical resection as the cornerstone of management.