Undifferentiated embryonal sarcoma (UES) of the liver is a very rare and highly malignant entity. UES has no specific clinical or laboratory features. At computed tomography images , the tumour typically appears as a large, predominantly cystic mass with well defined borders. This cystic appearance of UES can be cause a misdiagnosis with hydatid cyst very easily due to rarity of UES and more common seen hydatic cyst especially in endemic areas. We present a eight year old male case with cystic mass in liver, which was misdiagnosed and treated as hydatic cyst. Percutaneous sample was obtained .Cytological examination did not confirm the hydatid cyst. Because of progressive respiratory deterioration, urgent abdominal operation was performed. Gross haemorrhagic cystic lesion was discovered and evacuated. Pathological examination revealed UES. Because of pure cystic appearance of UEA in liver can be suggestive of benign similar pathologies , and cause delaying or misdiagnosis in such hydatic areas. Undifferentiated embryonal sarcoma (UES) of the liver is a very rare entity that was first described by Stocker and Ishak in 1978 (1,2). This rare neoplasm accounts for approximately 9% to 13% of all hepatic tumours in children (2). UES has no specific clinical or laboratory features, and fewer than 60 cases of paediatric UES have been reported in the literature (1). This cystic appearance of UES can cause the misdiagnosis of hydatid cyst very easily due to the rarity of UES, especially in endemic areas for hydatid cyst (3,4).

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