Background : Undifferentiated embryonal sarcoma of the liver((UESL) is a very rare primary hepatic tumor, of mesenchymal origin. Primary malignant mesenchymal tumors of the liver are relatively rare compared with carcinomas originating from hepatocytes or cholangiocytes. UESL is usually observed in children, and cases of adults are very uncommon. It was first reported in 1978. Because of rarity of the disease, there were few reported cases. Herein we report an our experience of UESL of the liver patient.

Methods : A 53-year-old woman visit our outpatient department presented with epigastric pain for 2 weeks. Huge complex cystic mass of the left liver(about 12cm) was identified on computed tomography(CT) of the abdomen. Compared with CT of 8 months ago, the size of the lesion was increased by 5 cm. Her laboratory study including tumor marker at initial presentation revealed no abnormal findings. We considered the lesion to be a complicated hepatic cyst. Since an increase in the size of the lesion was observed and she also had epigastric pain, we decided to proceed with surgery. We performed laparoscopic left hepatectomy.

Results : Microscopically, the tumor was composed of spindle cell proliferation, nuclear pleomorphism, myxoid stroma and frequent mitosis. The pathologic report revealed undifferntiated embryonal sarcoma. We initiated adjuvant chemotherapy 8 weeks after surgery.; MAID(Doxorubin,Dacarbazine,Ifosfamide, Mesna) for sarcoma. per 3 weeks, 6 cycles. Currently, the patient is doing well without recurrence of cancer after 8 months from liver resection.

Conclusions : This case presented as a cystic lesion in the liver and had typical histological features of UESL. It is a rare case of a malignant pediatric tumor occurring in an adult patient. We should consider the possibility of UESL when operating for a cystic mass of the liver.