Benign Bone Tumors

Benign tumors of bone are seen most frequently in skeletally immature or growing individuals. These tumors grow in a centrifugal fashion, as do their malignant counterparts, and, similarly, a reactive capsule (in this case, bone) is formed as the response of the host to the tumor. The extent of the reactive capsule reflects the rate at which the tumor is growing. Slowly growing tumors usually have a thick, well defined zone of transition, whereas those that are growing rapidly have a poorly defined or barely detectable zone. Because they lack histological uniformity, benign tumors of bone are graded on the basis of radiographic criteria. To distinguish them from the stages of malignant tumors, the stages of benign tumors are designated by Arabic numerals.

Latent benign bone tumors are classified as stage 1. Such tumors are usually asymptomatic and are commonly discovered as an incidental radiographic finding. Thick, dense reactive bone is present on both plain radiographs and computed tomography scans. These lesions remain dormant and heal spontaneously in many instances. Examples include fibrous cortical defects and non-ossifying fibromas. Operative treatment usually is not necessary.

Active benign bone tumors are classified as Stage 2; these tumors are actively growing and enlarging and therefore may be associated with physical signs and symptoms. In some instances, destruction of the cortex leads to a pathological fracture. A stage-2 tumor has a thin rim of reactive bone but remains intracompartmental. Examples include osteoid osteoma, simple bone cyst.

Locally invasive (aggressive benign) are classified as Stage 3, has little associated reactive bone and often breaks through the bone cortex. Stage-3 lesions are likely to be growing faster than are stage 1 or 2 lesions, and they are found both clinically and radiographically to be more locally invasive. Examples include giant cell tumor, aneurysmal bone cyst and chondroblastoma.


 

 

Stage

Definition

Behavior

1

Latent

Remains static or heals
spontaneously

2

Active

Progressive growth but limited by
natural barriers

3

Locally invasive

Progressive growth, not limited
by natural barriers.

 


Unicameral Bone Cyst in the calcaneus

Aneurysmal Bone Cyst of the proximal humerus

Multiple osteochondromatosis
Giant
cell tumor of the distal tibia with soft tissue
extension