Ewing Sarcoma FactFile

Overview of Ewing Sarcoma

Malignancy: Rare

Type of bone tumour: Primary

Grade: high (aggressive type)

Location:

Long bones e.g. femur.
Pelvis.
Ribs
Vertebrae (Spine)
Soft tissues (muscle, tendons, ligaments, tissues around joints, nerves, fat, blood vessels, deep skin tissues).

Onset: First three decades (Within 30 years) – children, teenagers, and young adults.

Median age at diagnosis: 15 years

Appearance: Onion skin

Risk Factors Of Ewing Sarcoma

A) Genetics:

The rearrangement between FET or TET family genes AND the ETS family genes to form a FUSION

The most common example of FET or TET family gene is the EWSR1 on chromosome 22 (22q12) (95% of cases)

AND

The most common example of the ETS family gene is FLI1 on chromosome 11.

This forms a fusion EWSR1:FLI1 on chromosome 11.

This fusion occurs in 95% of cases (Gerrand et al 2024).

Some sources suggest 85% of cases (Biermann et al. 2025).

Other Examples Of Genetic Fusions

There are other examples of FET: ETS gene fusions (5 to 10% of cases)

EWSR1 with the other ETS gene family (ERG, FEV, ETV1, ETV4)

Rare cases of Genetic Fusions

FUS of the FET/TET replaces EWSR1 and no EWSR1 rearrangement takes place.

t (16;21) (p11; q24) à FUS: ERG fusion

Other risk factors of Ewing Sarcoma

B) Gender:

Males are more at risk (1.5) compared to females (1). This gives a ratio of (1.5:1)

C) Ethnicity:

More common in other ethnicities than in Chinese and Afro-Caribbean.

Appearance Under Microscope

Cell Morphology: small, round, blue cell malignancy

Surface markers: High expression but not specific for Ewing Sarcoma

is cell surface glycoprotein MIC2 (CD99).

Microscopic image of Ewing Sarcoma (University of Singapore, 2026)

References

Bădilă, A.E., Rădulescu, D.M., Niculescu, A.-G., Grumezescu, A.M., Rădulescu, M. and Rădulescu, A.R. (2021). Recent Advances in the Treatment of Bone Metastases and Primary Bone Tumors: An Up-to-Date Review. Cancers, [online] 13(16), p.4229. Doi: https://doi.org/10.3390/cancers13164229.

Biermann, J.S., Hirbe, A., Ahlawat, S., Bernthal, N.M., Binitie, O., Boles, S., Brigman, B., Callan, A.K., Cipriano, C., Cranmer, L.D., Davis, J., Donnelly, E., Ferguson, M., Graham, A., Groundland, J., Hess, M., Hiniker, S.M., Hoover-Regan, M.L., Hornick, J.L. and Jonard, B. (2025). Bone Cancer, Version 2.2025, NCCN Clinical Practice Guidelines in Oncology. Journal of the National Comprehensive Cancer Network, [online] 23(4). does: https://doi.org/10.6004/jnccn.2025.0017.

Cancer Research UK (2025a) Types of bone cancer. Available at: https://www.cancerresearchuk.org/about-cancer/bone-cancer/types (Accessed 3^rd April 2026)

Cowan, P., Launico, M. and Kahai, P. (2024) Anatomy, Bones. Available at: https://www.ncbi.nlm.nih.gov/books/NBK537199/ (Accessed: 9^th April 2026)

Gerrand, C., Amary, F., Anwar, H.A., Brennan, B., Dileo, P., Kalkat, M.S., McCabe, M.G., McCullough, A.L., Parry, M.C., Patel, A., Seddon, B.M., Sherriff, J.M., Tirabosco, R. and Strauss, S.J. (2024). UK guidelines for the management of bone sarcomas. British Journal of Cancer. doi:https://doi.org/10.1038/s41416-024-02868-4.

Hosseini, H., Heydari, S., Kiavash Hushmandi, Salman Daneshi and Rasoul Raesi (2025). Bone tumors: a systematic review of prevalence, risk determinants, and survival patterns. BMC Cancer, 25(1). doi:https://doi.org/10.1186/s12885-025-13720-0.

National University of Singapore (2026) Clavicle Ewing Sarcoma. Available at: https://medi cine.nus.edu.sg/pathweb/virtual-pathology-museum/03515-2/ (Accessed: 16^th April 2026)

Pullan, J.E., and Lotfollahzadeh, S. (2024) Primary Bone Cancer Available at: https://www.ncbi.nlm.nih.gov/books/NBK560830/ (Accessed: 9^th April 2026)

‌WHO Editorial Board. WHO classification of bone tumours. In WHO Classification of Tumours Editorial Board. Soft tissue and bone tumours. Bovee J, Flanagan AM, Lazar AJ, Nielsen GP and Yoshida A (eds) pp 338. International Agency for Research on Cancer (2020)