Bone and soft tissue sarcomas represent about 7-12% of all pediatric cancer and are a heterogeneous group of tumors arising in connective tissues embryologically derived from the mesenchyme. For some of these tumors relapse and mortality rates are still significantly high. Therefore, further studies are needed to better understand pathogenetic processes underlying sarcomas to offer new and more effective treatments. Next generation sequencing (NGS) has opened new frontiers for cancer research allowing to identify somatic or constitutional mutations known or yet unknown with the aim to better understand carcinogenesis. The establishment of the genomic profile of the tumor could also help clinicians to personalize patients treatment based on their genetic and molecular alterations.

Inclusion Criteria:

1. Patients with histologically confirmed Osteosarcoma, Ewing Sarcoma or Synovial Sarcoma at first diagnosis.
2. Patients with confirmed relapsed/refractory Osteosarcoma, Ewing Sarcoma or Synovial Sarcoma
3. Written informed consent signed by the patient, or parents or legal representative to perform molecular analysis of the tumor sample.
4. Patients aged ≤24 years
5. Pathological review of tumor samples.
6. Availability of fresh tumor sample from newly diagnosed or relapsed/refractory cancer and 10 ml of EDTA peripheral blood sample. Centralization of paraffin-embedded tumor sample might be optional.

Exclusion Criteria:

• 1. Known history of active HIV, HCV, or HBV infection 2. Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient undergoing surgery biopsy or the quality of the data.

Children, adolescents and young adults aged ≤ 24 years with newly diagnosed or relapsed/refractory Osteosarcoma, Ewing Sarcoma or Synovial Sarcoma.