Integrated multimodal genetic testing of Ewing sarcoma--a single-institution experience

Area of Science:

• Oncology
• Molecular Diagnostics
• Pediatric Cancer Research

Background:

• Ewing sarcoma (ES) is an aggressive small round cell tumor common in adolescents and young adults.
• Characteristic molecular hallmark is EWSR1 gene fusion with ETS family genes, primarily FLI1 and ERG.

Purpose of the Study:

• To evaluate the utility of integrated clinicopathologic, cytogenetic, FISH, and RT-PCR analyses for diagnosing ES.
• To assess the detection rates and limitations of each diagnostic method for EWSR1 rearrangements.

Main Methods:

• Retrospective analysis of 32 pediatric ES patients diagnosed between 2005-2011.
• Utilized conventional cytogenetics, fluorescence in situ hybridization (FISH), and reverse transcriptase polymerase chain reaction (RT-PCR).
• Sanger sequencing was employed to delineate breakpoints in RT-PCR positive cases.

Main Results:

• EWSR1 rearrangements detected in 93.8% of patients.
• Cytogenetics identified t(11;22) in 14 cases and t(21;22) in 1 case.
• FISH detected rearrangements in 96.4% of tested patients, while RT-PCR was positive in 84.4%, identifying EWSR1-FLI1 and EWSR1-ERG fusions.

Conclusions:

• Conventional cytogenetics offers a global view but has lower detection rates and longer turnaround times.
• FISH is rapid but lacks specificity and partner identification.
• RT-PCR and sequencing are sensitive for identifying fusion partners and breakpoints but depend on RNA quality.