Pediatric soft tissue sarcoma is made up of different subtypes, some of which have distinct genetic alterations. Fusion variants were found in about 43% of bone and soft tissue sarcoma samples. Ewing sarcoma is characterized by recurrent chromosome translocation, with up to 95% of cases showing EWS-ETS translocation. The genetic features of the tumor can change as it spreads or shrinks, and can also be influenced by treatment.

To better understand treatment response and predict relapse early, our study collects liquid samples such as blood, bone marrow, or cerebrospinal fluid at various points during treatment. We then use next-generation sequencing to dynamically monitor the unique genetic profile of the tumor. Additionally, our research may identify new genetic targets and suggest potential treatment options.

Inclusion Criteria:

• (1) pediatric patients with soft tissue sarcoma confirmed by pathology(including but not limited to rhabdomyosarcoma, Ewing sarcoma, BCOR rearrangement undifferentiated sarcoma, CIC rearrangement undifferentiated sarcoma, Epithelioid sarcoma and synovial sarcoma.
• (2)younger than 18 years old.
• (3)ECOG status: PS score0-2.
• (4)measurable lesions on CT/MRI according to RECIST 1.1 criteria : long diameter≥10mm; the longest diameter on ≥ one lymphnode ≥1.5 cm.
• (5)sufficient clinical and pathological information.
• (6)candidates can receive evaluation on time and provide samples during the trials.
• (7)candidates should be informed and provide informed consents.

Exclusion Criteria:

• Sufficient samples at baseline point can not be obtained including pre-operation plasma, tissues, bone marrow aspirate and cerebrospinal fluid.
• Plasma samples can not be obtained during monitoring.
• Ineligible candidates at the discretion of researchers.

Asian population predominates