Clinicopathological characteristics and genetic features of young and senior Ewing sarcoma patients

Ewing sarcoma (EwS) is a highly malignant and heterogeneous tumor. Exploring clinicopathological characteristics and genetic features of EwS is critical for prognosis and treatment regimen. Clinicopathological characteristics and genetic features of young (≤ 30y) and senior (> 30y) EwS patients were analyzed based on histology, phenotype, and next-generation sequencing (NGS) detection. The young group (18/36) presented nontypical EwS histological morphology, whereas the senior group (18/36) presented typical morphology. The prognosis of the young group was found to be worse compared with the senior group for patients without metastasis at the initial diagnosis. DNA- and RNA-based NGS was conducted on 20 extraosseous EwS patients. 16/20 samples demonstrated EWSR1-FLI1 fusion and 4/20 demonstrated EWSR1-ERG fusion. However, 13/16 EWSR1-FLI1fusions were detected both in DNA- and RNA-based NGS, 1/16 was detected only at the DNA level, and 2/16 were detected only at the RNA level. An analysis of the genetic profiles of the EWSR1-FLI1 cases revealed that the young group was inclined to couple with more copy number variations (CNV), such as CCND1, CDK4 amplification, and fusion variations, such as CHEK1-EWSR1, SLIT2-EWSR1, and EWSR1-FAM76B fusion. The senior group was more likely to have SNV or Indel mutations, such as EPHA3 and STAG2 mutations. Moreover, patients with more CNV abnormalities had a worse prognosis than those with predominantly SNP variants. In addition, compared with the senior group, the young group had significantly higher CyclinD1 protein expression. Clinicopathological characteristics and genetic features in young and senior EwS patients differed significantly. Targeting cell cycle dysregulation based on age subgroup may be a potential therapeutic strategy for Ewing sarcoma.