Bone island

 

Bone island hip 2Bone island hip

 

Definition

 

Enostosis

 

Benign sclerotic lesion

 

Island of mature cortical bone found in the midst of normal cancellous bone

 

Clinical

 

Asymptomatic x-ray finding

Need to consider metastatic disease in the differential

 

X-ray

 

Shoulder Bone IslandBone island shoulder

 

Sharply-circumscribed cortical densities

- round or oval in shape with smooth, regular borders

- narrow zone of transition from lesion to cancellous bone 

- no evident reaction to the process

 

Usually < 1 cm in diameter

 

> 2 cm - giant bone island

 

CT 

 

Even cortical texture

 

CT bone island

 

Shoulder bone island CT

 

MRI

 

- Low signal on T1 and T2

- Do not enhance with contrast

 

MR bone island 1MRI bone island 2

 

Bone island 3Bone island 2Bone island 1

 

Management

 

Observation

 

Osteopoikilosis 

 

Rare inherited benign condition characterised by multiple bone islands

 

AD inheritance, high penetrance

 

Lesions clustered around joints

- typically arms, legs and pelvis

 

Malignant transformation extremely rare

 

Differential diagnosis

- sclerotic metastasis

- osteopoikilosis cold on bone scan