Abstract： Objective To analyze the clinical characteristics and prognosis of rare soft tissue sarcomas.Method Clinical data of 51 patients with rare soft tissue sarcomas including fibrosarcoma,synovial sarcoma,extrarenal rhabdoid tumor,alveolar soft part sarcoma,desmoplastic small round cell tumor and undifferentiated sarcoma in children and adolescents,diagnosed at Shanghai Children's Medical Center from June 1998 to December 2013,were retrospectively analyzed.All types were treated with the same strategy and chemotherapy regimens.Their clinical features,treatment and prognosis were discussed.Result Seventeen patients with fibrosarcoma,10 with synovial sarcoma,9 with extrarenal rhabdoid tumor,6 with alveolar soft part sarcoma,3 with desmoplastic small round cell tumor and 6 with undifferentiated sarcoma were included.The mean age at initial diagnosis was 5 years(range from 1 month to 13.5 years).The most common primary site of tumors was limbs,followed by the thoracic and abdominal cavity,accounting for 41％ and 24％ respectively.Twelve cases presented distant tissue or organ involvement in which bone metastases occupied the first place.Seven cases(accounting for 14％)were at stage Ⅰ,13 cases were at stage Ⅱ (accounting for 25％),19 cases were at stage Ⅲ (accounting for 37％) and 12 cases were at stage Ⅳ (accounting for 24％).The median follow-up period was 36 months(range from 1 month to 123 months).Forty-four patients achieved complete remission and 3 patients achieved partial remission after initial treatment,the overall response rate was 92％.Subsequent follow-up showed 29 patients remained relapse-free while 13 patients had relapsed disease.Overall survival and event-free survival at 2 years were 88％ and 57％.Postoperative surgical staging was the main prognostic factors.Patients with stage Ⅲ + Ⅳ had poorer results than those with Ⅰ + Ⅱ (x2 =4.909,P =0.027).Conclusion These 6 types of soft tissue sarcomas are rare in children and adolescents.The tumor can occur anywhere in the body but commonly presents in the extremities.Complete resection of tumor remains the most important modality of treatment and is directly related to prognosis.Neoadjuvant chemotherapy helps improve the resection rate of some unresectable tumors at diagnosis.Radiation therapy is primarily adopted for focal tumor control.