Undifferentiated Small Round Cell Sarcomas: Radiologic-Pathologic Correlation for the Updated WHO Classification...

Area of Science:

• Oncology
• Pathology
• Radiology

Background:

• The World Health Organization (WHO) revised bone and soft-tissue tumor classification in 2020.
• Previously grouped Ewing sarcoma family tumors are now categorized as undifferentiated small round cell sarcomas.
• This reclassification is based on distinct molecular genetic characteristics.

Purpose of the Study:

• To outline the four newly defined entities within undifferentiated small round cell sarcomas.
• To describe the unique clinical, pathologic, and imaging features of each subtype.
• To discuss the implications for diagnosis, treatment, and prognosis.

Main Methods:

• Review of the 2020 WHO classification of bone and soft-tissue tumors.
• Analysis of clinical, pathologic, and imaging characteristics for each entity.
• Comparison of treatment responses and prognoses among the subtypes.

Main Results:

• Four distinct entities are identified: Ewing sarcoma (ES), CIC-rearranged sarcoma, sarcoma with BCOR genetic alterations, and sarcoma with EWSR1-non-ETS fusion genes.
• Each subtype exhibits specific radiologic findings, such as bone destruction patterns, soft-tissue mass characteristics, and calcification.
• Radiologic recognition can inform treatment strategies and prognostic expectations.

Conclusions:

• Accurate classification of these sarcomas is crucial for appropriate management.
• Imaging plays a vital role in differentiating these subtypes, guiding therapeutic decisions.
• Understanding the distinct features of each entity improves patient care and outcomes.