Cystic undifferentiated sarcoma of liver in children: a pitfall diagnosis in endemic hydatidosis areas.

Undifferentiated (embryonal) sarcoma (UES) of the liver is a very rare pediatric neoplasm with an aggressive behavior. Multimodal treatment including complete surgical resection and chemotherapy has improved survival. We report a case of UES occurring in a 15-year-old female. Radiographic findings showed a multicystic mass appearance. The diagnosis of hydatid cyst was initially presumed. A complete tumor resection after 3 cycles of chemotherapy was performed. Histologically, only 20% of tumor necrosis was noted. Adjuvant chemotherapy was instituted. She remained well at 11 months of follow-up. Cystic appearance is a usual finding in UES. Differential diagnosis with hydatid cyst may be problematic in endemic hydatidosis areas.