Osteoma

An osteoma is a benign bone growth that often appears on imaging studies performed for other reasons. These growths develop slowly, are usually painless, and most commonly occur in the skull and facial bones. Because they are non-cancerous, osteomas rarely cause problems, but their presence on a radiology report can be confusing or concerning if you are unfamiliar with the term. Imaging plays a central role in detecting, confirming, and monitoring osteomas.

What is an Osteoma?

An osteoma is a non-cancerous tumor made of mature bone tissue. Unlike more aggressive bone lesions, it remains well-contained, grows very slowly, and does not spread to other parts of the body. Osteomas are typically located on the surface of bones (known as exophytic growths), but some can develop inside bone cavities, especially in the paranasal sinuses.

They are most common in adults and can occur as a single isolated growth. In rare cases, multiple osteomas may be seen, sometimes as part of genetic syndromes such as Gardner’s syndrome.

Osteoma on X-ray

X-rays are often the first imaging test where an osteoma might be noticed. On plain radiographs, osteomas appear as bright, dense spots with smooth, rounded borders. Their density is similar to that of compact bone, which makes them stand out from the surrounding structures. While X-rays can suggest an osteoma, they do not always show detailed relationships to nearby anatomy, so more advanced imaging is often recommended.

Osteoma on CT Scan

CT (Computed Tomography) is the best imaging method for evaluating osteomas. CT provides highly detailed cross-sectional views of bone, allowing radiologists to assess the size, exact shape, and precise location of the lesion.

On CT, an osteoma appears as a very dense, well-defined bone growth, often projecting outward from the skull or sinus wall. CT also helps determine whether the growth is affecting sinus drainage pathways, encroaching on the orbit (eye socket), or pressing against nerves.

Osteoma on MRI

MRI (Magnetic Resonance Imaging) is less effective than CT for visualizing osteomas because bone tissue shows up as very dark (signal void) on MRI scans. However, MRI can be useful for evaluating the soft tissues surrounding the lesion. For example, MRI can help confirm that the osteoma is not associated with abnormal soft tissue growth or inflammation.

Other Imaging Methods

• Ultrasound: Occasionally, very superficial osteomas may be detected on ultrasound, especially if they are close to the skin. This is uncommon, as ultrasound is not a standard tool for bone imaging.

• Follow-up Imaging: In most cases, osteomas remain stable. Repeat scans may only be recommended if the lesion is large, in a sensitive location, or if there are new symptoms such as headaches or sinus blockage.

Imaging Features of Osteomas

Osteomas have distinct features that make them relatively easy to identify on scans:

• They are well-defined and have smooth borders.

• Their density matches that of mature bone.

• They do not invade surrounding tissues.

• Growth, if any, is slow and usually not clinically significant.

Common Locations of Osteomas Seen on Imaging

• Frontal sinus: The most common location. Often discovered when patients undergo CT scans for sinus problems or head trauma.

• Ethmoid or maxillary sinuses: Less common, but can cause sinus drainage obstruction if large.

• Skull vault: Small nodules may appear on the outer surface of the skull, often noticed during scans for unrelated conditions.

• Mandible (jawbone): Sometimes found during dental imaging.

Clinical Importance of Imaging Osteomas

The primary role of imaging is to confirm the diagnosis and differentiate osteomas from other bone lesions. Some conditions that can mimic osteomas include osteoid osteoma, fibrous dysplasia, ossifying fibroma, or, rarely, malignant bone tumors. CT’s ability to show detailed bone architecture makes it the most reliable method for distinguishing osteomas from other conditions.

In most cases, no treatment is required. Surgery may be considered if the osteoma causes symptoms such as sinus obstruction, facial pain, cosmetic deformity, or compression of important structures. Even then, the decision is usually based on clinical symptoms rather than imaging alone.

What Patients Should Ask After an Osteoma Diagnosis

When an osteoma is mentioned in a radiology report, patients often feel uncertain about whether it needs to be addressed. Helpful questions include:

• Where exactly is the osteoma located?

• Could it interfere with sinus function, vision, or nerves?

• Is follow-up imaging recommended, or can it simply be observed?

• What symptoms should I watch for?

• Under what circumstances would surgery be considered?

Conclusion

An osteoma on a radiology report is almost always a harmless finding. CT scans provide the clearest and most reliable assessment of these bone growths, while MRI and X-rays may give additional supporting information. Most osteomas are small, stable, and require no treatment, offering reassurance to patients. Follow-up may be suggested only in specific cases where symptoms develop or the growth is in a sensitive area. With proper imaging, osteomas can be confidently diagnosed and safely monitored.

References

https://radiopaedia.org/articles/osteoma

https://pmc.ncbi.nlm.nih.gov/articles/PMC3451122/

https://pmc.ncbi.nlm.nih.gov/articles/PMC10477812/