Abstract
INTRODUCTION: Undifferentiated embryonal sarcoma of the liver (UESL) is an exceptionally rare and aggressive malignancy, predominantly affecting children. Its occurrence in the elderly is exceedingly uncommon, posing significant diagnostic challenges. We present the oldest-reported case of UESL, initially misdiagnosed as intrahepatic cholangiocarcinoma (iCCA). PRESENTATION OF CASE: An 88-year-old male presented with an upper abdominal mass and discomfort. Imaging (CT/MRI/PET-CT) and mildly elevated CA19-9 initially suggested iCCA (T1bN0M0, Stage IB). After 10 months of disease progression despite chemotherapy (capecitabine), left hemihepatectomy was performed. Histopathological examination revealed UESL (7.5 cm tumor; IHC: Vimentin+, CD10+, CD56+, Ki-67 80 %). The patient developed recurrent hepatic disease and pulmonary metastases 1.5 months postoperatively and succumbed to the disease shortly thereafter, with an overall survival of approximately one year. DISCUSSION: UESL in octogenarians is exceptionally rare, with nonspecific imaging and serological findings (e.g., mild CA19-9 elevation) leading to frequent misdiagnosis, often as iCCA. Pathological examination remains essential for definitive diagnosis. Despite radical resection, prognosis in elderly patients is poor due to aggressive biology and limited tolerance for adjuvant therapy. This case underscores the importance of considering UESL in atypical liver masses across all age groups. CONCLUSION: UESL should be included in the differential diagnosis of atypical liver masses, even in elderly patients. Early surgical resection offers the best chance for survival, though outcomes remain dismal in advanced age due to rapid recurrence and metastasis. Heightened awareness of this entity is crucial to mitigate diagnostic delays.