Periosteal chondroma (juxtacortical chondroma)

Tumor biology

• Rare, slow-growing, benign, generally active cartilage lesion
• Not known to metastasize
• Arises on the surface of bone with underlying cortical scalloping

Age

Second through fourth decades

Gender

M:F = 1:1

Presentation

• Pain, tenderness at site of lesion
• Often accompanied by swelling

Physical findings

Localized swelling may be present

Plain films

Site

• Lesion eccentric, subperiosteal in location, external to cortex
• Medullary canal not involved
• Most common site: metaphyseal cortex of long bones (especially proximal humerus and femur), small tubular bones of hands and feet

Size

Variable

Tumor effect on bone

• Periosteal-based soft tissue lesion
• Typically causes erosion/scalloping.

Bone response to tumor

• Lesion is well defined, shallow, geographic
• Sharp sclerotic interface with underlying eroded cortical margin
• Peripheral periosteal elevation and reaction may be seen
  
  
  

Matrix

• Scattered calcifications may be present
• Lesions may be highly calcified and radiopaque
  
  
  

Cortex

Cortical scalloping/erosion by the overlying juxtacortical mass

Soft tissue mass

Always present

Differential diagnosis

• Periosteal chondrosarcoma
• Periosteal osteosarcoma
• Soft tissue neoplasm eroding adjacent cortical bone
  
  
  

Pathology

• Gross: Cartilage nodules located on surface of cortex
• Microscopic: Hyaline cartilage showing variable cellularity
• Cytological atypia may be present; correlation with radiologic appearance critical
• New bone formation may be present at interface of lesion and underlying cortical bone
  
  
  

Diagnosis and treatment

• Treatment of choice: en bloc resection with an intact narrow rim of normal bone
• Curettage has relatively high risk of recurrence
• Spilling cartilage into soft tissues by curettage increases risk of local relapse