Radiographic appearance of a bone island (enostosis)

A coronal reformatted CT scan (A) shows a 2 mm bone island as a well-circumscribed sclerotic focus within the left proximal femur compatible with a benign bone island (arrow). Image B is an axial view of the lesion (arrow). Image C is a radiograph of a larger bone island in the right sacrum (arrow) shown on a CT in axial projection (D, arrow).