Primary undifferentiated embryonal sarcoma of the liver misdiagnosed as hydatid cyst in a child: a case report and review of the literature.

Primary undifferentiated embryonal sarcoma (UES) of the liver is a highly malignant mesenchymal origin tumor and has a peak incidence between the ages of 6 and 10 years. We hereby report a case of primary UES of the liver in a 7-year-old male patient who initially was misdiagnosed and treated as hydatid cyst of the liver. The tumor was occupying almost the entire right lobe of the liver and had a mostly cystic appearance with some solid components in it. Because hydatid disease is endemic in this region, it can often lead to misdiagnosis. The correct diagnosis was established after a biopsy and following neo-adjuvant chemotherapy the patient underwent a successful right hepatic lobectomy with complete resection of the tumor. The patient also received adjuvant chemotherapy and is currently disease-free in the present six month period. Primary UES of the liver has a predominantly solid appearance on US in contrast to its mostly cystic appearance on CT and MRI. These paradoxical imaging findings should be kept in mind in order to be able to distinguish this rare tumor from other entities, especially hydatid cyst. Thus, early diagnosis and prompt surgical resection of these tumors together with adjuvant and/or neo-adjuvant chemotherapy can provide complete remission.