Bone island: Meaning in a Radiology Report

Bone island

Also written as: enostosis, compact bone island, sclerotic bone island

A bone island is a small, benign spot of dense, compact bone inside normal bone. It shows as a white dot on X-ray or CT.

Seen on: X-ray, CT

How it reads in a report

A 6 mm sclerotic focus with brush-like margins in the left iliac bone, consistent with a bone island.

What it means

Most bone has a hard outer shell and a spongy, mesh-like inside. A bone island is a small patch of the hard type sitting within the spongy part. It is a benign quirk of bone development, not a disease. Bone islands are most common in the pelvis, thigh bone and ribs. Most are under 2 cm, with fine, brush-like edges that blend into the bone around them.

When it matters

Bone islands need no treatment and usually cause no symptoms. The radiologist's main job is to tell them apart from other dense spots. This matters most in people who have had cancer, because some cancers spread to bone as dense spots. A typical look and no change over time are reassuring. If a spot is large, growing or unusual, doctors may compare older scans, repeat the imaging or order a bone scan or MRI.

Questions to ask your doctor

Does it have the typical look of a bone island?
Can older scans confirm that it has not changed?
Given my medical history, does it need a bone scan or follow-up?

General information, not medical advice. What a finding means for you depends on your symptoms, your history and the images themselves, so talk your results through with a doctor.