[Ewing sarcomas and Ewing-like sarcomas : New aspects].

Area of Science:

• Oncology
• Molecular Pathology
• Genetics

Background:

• Ewing family of tumors (EFTs) are aggressive pediatric and young adult neoplasms.
• Classical EFTs feature specific gene fusions (EWSR1/FUS with ETS family genes).
• Ewing-like sarcomas and undifferentiated round cell sarcomas exhibit distinct genetic alterations and broader morphology.

Purpose of the Study:

• To review the molecular landscape of EFTs and related entities.
• To highlight diagnostic complexities arising from heterogeneous genetic profiles and morphology.
• To emphasize the need for advanced molecular diagnostics in classifying these rare tumors.

Main Methods:

• Review of genetic rearrangements in EFTs and related sarcomas.
• Analysis of morphologic spectrum and immunohistochemical profiles.
• Discussion of molecular work-up strategies including gene fusion detection.

Main Results:

• Classical EFTs are defined by EWSR1/FUS-ETS gene fusions.
• Ewing-like sarcomas involve EWSR1 rearrangements with non-ETS genes.
• Undifferentiated round cell sarcomas include CIC-DUX4 fusions or BCOR alterations, presenting unique gene expression signatures.
• Morphologic and immunohistochemical features (e.g., CD99 positivity) can be inconsistent, complicating diagnosis.

Conclusions:

• Accurate diagnosis of EFTs and related round cell sarcomas requires a comprehensive molecular approach.
• Distinct molecular subgroups necessitate further investigation for targeted therapies.
• Ongoing research aims to refine molecular subclassification for improved patient management.