Osteoid Osteoma FactFile

Overview of Osteoid Osteoma

Malignancy: Benign

Type of bone tumour: Primary

Grade: Low

Location:

It mainly occurs in the long bones.

Upper limbs and hands: Humerus (arms), fingers (phalanges)

Lower limbs: Proximal femur, tibia, feet (phalanges)

Posterior of spine (vertebrae)

Onset: First two decades (5 to 25)

Risk Factors Of Osteoid Osteoma

A) Genetics:

Adenomatous Polyposis Coli (APC) gene on chromosome 5 mutation

Gardner’s syndrome: A form of polyps found in the colon (part of the large intestine) and also osteomas in the skull and jaws (mandible)

APC. A healthy colon becomes hyperplastic when there is overgrowth of cells. This leads to the formation of structures or overgrowths called polyps, where some can increase in size over time, arising from the glandular tissue and forming benign cancers. They are not harmful, but need to be monitored if they increase in size because it can lead to the formation of adenocarcinoma or colorectal cancer. Polypectomy is the surgical removal of polyps.

signs of Gardner’s syndrome through X-ray analysis.

Other risk factors of Osteoid Osteoma

B) Injury e.g. trauma

C) Inflammation

D) Abnormal growth of cells in the region, e.g., neoplasia

Appearance Under Microscope

Cell Morphology:

There is a Nidus

Sharp, round, or oval lesion less than 2cm
1 to 2 mm peripheral radiolucent zone
The centre of the nidus may be calcified.

Diaphysis – dense bones, thick lining (cortex)

Metaphysis – less thickness in the compact bone

Intermediate magnification view of a nidus of osteoid osteoma showing irregular anastomosing trabeculae of woven bone surrounded by loose fibrovascular tissue containing numerous benign multinucleated giant cells. The trabeculae are lined by well-differentiated osteoblasts lacking the atypia or mitotic activity associated with osteosarcomas.

References

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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.

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)

Web Pathology (2026) Osteoid Osteoma: Microscopic Features. Available at: https://www.webpathology.com/images/orthopedic/bone-tumors—ii/osteoid-osteoma/58622 (Accessed: 17^th July 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)

Updated July 2026 Next Review July 2028