Bony Lesions / Bone Tumor
Bone lesions should not be defined radiographically as malignant or benign, but rather aggressive or nonaggressive. Some malignant lesions can have a nonaggressive appearance and many benign lesions can have a very aggressive appearance.
Criteria that should be assessed when evaluating a bony lesion:
Demographics: lesions of bone have a specific propensity based on age and occasionally gender
Location: the location of the lesion within the skeleton is critical because specific lesions have a propensity to affect certain locations in the skeleton.
Longitudinal location: Most common tumor sites:
• Epiphysis: chondroblastoma, giant cell tumor (GCT), aneurysmal bone cyst (ABC). GCT and ABC usually arise from the metaphysis and extend into the epiphysis.
•Metaphysis: osteochondroma, chondrosarcoma, nonossifying fibroma, enchondroma (long bones), osteosarcoma, chondromyxoid fibroma, ABC, GCT.
•Diaphysis: enchondroma (phalanges), osteoid osteoma, osteoblastoma, Ewing’s sarcoma, fibrous dysplasia.
Axial location: The location of the lesion should be defined as central intramedullary, eccentric intramedullary, cortically based, or surface (periosteal) centered.
Zone of transition: the transition zone between the lesion and the adjacent uninvolved bone should be classified as:
•Narrow: well-defined margins that can be traced out with a pencil. This is a nonaggressive feature.
•Wide or ill-defined: poorly defined margins, not easily traceable with a pencil. This is an aggressive feature.
Pattern of bone destruction: the pattern of bone replacement should be assessed and characterized as:
•Geographic: well-defined lesion of bone. Geographic lesions have a narrow zone of transition by definition. This is a nonaggressive feature.
•Blastic or sclerotic: densely sclerotic lesion of bone. Can be aggressive or nonaggressive
•Permeative: ill-defined bony destruction. This is an aggressive feature.
•Bubbly: multilocular lucencies, with or without expansile appearance. This is usually a nonaggressive feature.
Presence of matrix: If present, matrix falls into one of following categories:
Types of Nonaggressive Primary Bone Tumors by Matrix Appearance:
Unicameral bone cyst
Aneurysmal bone cyst
Giant cell tumor
Important determinators in the analysis of a potential bone tumor are:
The morphology of the bone lesion on a plain radiograph
The age of the patient
--> the plain radiograph is the most useful examination for differentiating these lesions.
CT and MRI are only helpful in selected cases.