Undifferentiated Embryonal Sarcoma of the Liver Identified after the Initial Diagnosis of a Hepatic Cyst.

Abdominal ultrasound in a 50-year-old Japanese man revealed a cystic lesion on the caudate lobe of the liver. Four-month follow-up imaging showed a rapid increase in the size of the cystic lesion. The patient underwent laparoscopic partial hepatectomy because of a suspicion and perceived risk that the lesion might be malignant. The initial histological diagnosis was a hepatic cyst. Eleven months later, computed tomography showed a giant cystic lesion in the abdominal cavity and multiple liver metastases. The patient underwent excision of the giant cystic lesion and a partial hepatectomy. Immunohistochemistry for the recurring lesion revealed undifferentiated embryonal sarcoma of the liver.