Ewing's sarcoma pathophysiology
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Ewing's sarcoma Microchapters |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Michael Maddaleni, B.S.
Overview
Ewing sarcoma may occur anywhere in the body, but most commonly in the pelvis and proximal long tubular bones. The pathogenesis of Ewing sarcoma include t(11;22) chromosomal translocation. On microscopic histopathological analysis, presence of small round cells that have a high nuclear to cytoplasmic ratio, vacuolated cytoplasm, and faded boundaries are characteristic findings of Ewing sarcoma.
Pathophysiology
Ewing sarcoma may occur anywhere in the body, but most commonly in the pelvis and proximal long tubular bones. The diaphyses of the femur are the most common sites, followed by the tibia and the humerus.
Genetics
Ewing sarcoma is the result of a translocation between chromosomes 11 and 22, which fuses the EWS gene of chromosome 22 to the FLI1 gene of chromosome 11.
- The EWSR1 gene is a member of the TET family [TLS/EWS/TAF15] of RNA-binding proteins. The FLI1 gene is a member of the ETS family of DNA-binding genes.
- Characteristically, the amino terminus of the EWSR1 gene is juxtaposed with the carboxy terminus of the ETS family gene.
- In most cases (90%), the carboxy terminus is provided by FLI1, a member of the family of transcription factor genes located on chromosome 11 band q24.
- Other family members that may combine with the EWSR1 gene are ERG, ETV1, ETV4 (also termed E1AF), and FEV.
- Rarely, TLS, another TET family member, can substitute for EWSR1.
Microscopic pathology
Ewing sarcoma is a small round blue cell tumor with regular sized primitive appearing cells:
- It consists of a homogeneous population of small round cells that have a high nuclear to cytoplasmic ratio.
- The population of small round cells are arrayed in sheets.
- There is a presence of scant cytoplasm which are pale, vacuolated, and are characterized by their faded boundaries.[1]
- The nuclei have intense color which make them easily visible.
- Cytoplasmic glycogen is also usually present.
References
- ↑ Iwamoto Y (2007). "Diagnosis and treatment of Ewing's sarcoma". Japanese Journal of Clinical Oncology. 37 (2): 79–89. doi:10.1093/jjco/hyl142. PMID 17272319. Retrieved 2012-01-04. Unknown parameter
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