Undifferentiated embryonal sarcoma of the liver is the 3rd most common malignant liver tumor after hepatoblastoma and hepatocellular carcinoma with a peak incidence between 6 and 10 years of age. Historically, it is a tumor treated only by surgery with a poor prognosis. In the last decade, the combination of more intensive chemotherapy and, more randomly, radiotherapy, has significantly improved the survival rate of these patients. Due to its low incidence, there are few series reported in the literature and to date there is no specific treatment protocol for the management of these tumors.

It seems appropriate to review the management of these tumors in France in order to discuss the best therapeutic strategy.

Inclusion criteria:

• Any patient aged 0 to 25 on the date of inclusion in the study
• Treatment carried out in France (included in NRSTS 2005, in the childhood cancer registry or in an SFCE center)
• Start of treatment from 01/01/2008 to 31/12/2018
• Diagnosis of undifferentiated embryonal sarcoma of the liver defined by a compatible histological analysis
• Adult subject who has not expressed, after being informed, his opposition to the reuse of his data for the purposes of this research
• Minor subject (and/or his parental authority) who has not expressed, after being informed, his opposition to the reuse of his data for the purposes of this research

Exclusion criteria:

• Refusal to participate in this research
• Diagnosis of rhabdoid tumor, rhabdomysarcomas, angiosarcomas, PNET
• Absence of histological and/or molecular documentation.

Patient aged 0 to 25 with treatment carried out in France from 01/01/2008 to 31/12/2018