Definition 

Ectopic rest of cortical bone

Epidemiology

Common in all age groups

Site

Any bone can be affected, but they are more common in the pelvis and proximal femur, and the ribs.

Clinical

Asymptomatic

Radiology

Single or multiple intraosseous lesions, homogenous, with radiating spicules extending from the centre of the lesion.  They are usually less than 2cm in size but may reach up to 5cm.

MRI: low signal intensity in all sequences.

Bone scan: do not light up, except in cases of giant bone islands.

Histology

Cortical bone

Management

Observation.  If otherwise typical lesions increase in size by more than 25% over 6 months, they should be biopsied to rule out a low-grade osteosarcoma.

Osteopoikilosis

This is a rare, autosomal dominant condition characterized by multiple bone islands.

The disease is symmetrical, and tends to involve the epiphyses and metaphyses, and the small bones of the hands and feet.

The disease is symptomless and is usually an incidental finding.