Undifferentiated sarcoma of the liver: Multicenter international experience of the Cooperative Soft-Tissue Sarcoma Group and Polish Paediatric Solid Tumor Group.

Background Undifferentiated embryonal sarcomas of the liver (UESL) are extremely rare and continue to pose a diagnostic and therapeutic challenge. The aim of the study was to present a multicenter experience of the German CWS and Polish PPSTG groups in the treatment of UESL in children. Procedure Twenty-five patients were treated according to the CWS-96, CWS-2002, and CYVADIC protocols. Distant metastases were observed in four cases (16%). In four cases, an initial disease presentation mimicked other entities. A pure cystic appearance of liver mass led to misdiagnosis of hydatid cyst in three cases. In one case, laparotomy was performed due to the signs of appendicitis, and bleeding from ruptured liver tumor was found. All these patients were finally diagnosed as UESL. Results Thirteen patients received preoperative chemotherapy. Partial response was observed in 10 cases. Tumor resection was performed in 20 patients (primary resections, 12; delayed resections-, 8). In five patients, the primary tumor never became operable. The macroscopically complete resection rate was 95% (19/20). Postoperative chemotherapy was given to 20 children. Local radiotherapy was used in three children. After a median follow-up time of 136 months, 17 patients (68%) were alive with no evidence of disease. All children with unresectable tumor and three out of four patients with distant metastases died. The five-year overall survival (OS) rate was 72%. Conclusions In summary, a complete tumor excision plays the central role in the treatment of UESL. A cystic presentation of the liver lesion on imaging does not exclude the diagnosis of malignant tumor.