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Introduction
  • A benign chondrogenic tumor composed of hyaline cartilage
    • located in the medullary cavity 
    • caused by an abnormality of chondroblast function in the physis
  • Epidemiology
    • incidence
      • 2nd most common benign cartilage lesion (osteochondroma is most common)
    • demographics
      • male:female ratio is 1:1
      • age bracket
        • most common in 20-50 year olds
      • location
        • usually found in the medullary cavity of the diaphysis or metaphysis
        • the most common locations hand (60%) > feet
          • the most common bone tumor in the hand is the enchondroma
        • other locations include distal femur (20%) > proximal humerus (10%) > tibia
        • rare in the pelvis, scapula, ribs
          • suspect chondrosarcoma in these locations
  • Pathophysiology
    • enchondromas represent incomplete endochondral ossification
      • chondroblasts and fragments of epiphyseal cartilage escape from the physis, displace into the metaphysis and proliferate there 
  • Associated conditions
    • solitary enchondroma
    • Ollier's disease (multiple enchondromatosis)  
      • sporadic inheritance with no genetic predisposition
      • skeletal dysplasia with failure of normal endochondral ossification 
      • enchondromas throughout the metaphyses and diaphyses of long bones
        • involved bones are dysplastic, with shortening and bowing
      • risk of malignant transformation <30%
    • Maffucci's syndrome 
      • sporadic inheritance with no genetic predisposition 
      • multiple enchondromas and soft-tissue angiomas   
      • radiographically, enchondromas in Maffucci's syndrome markedly expand the bone and angiomas are seen as small, round calcified phleboliths
      • risk of malignant transformation up to 100% 
      • also has increased risk of visceral malignancies (astrocytoma, GI malignancy)
Classification
 
Enneking Classification of Benign Lesions
Stage Grade Examples
Images 
Stage 1 Latent lesions enchondroma, non-ossifying fibroma  
Stage 2 Active lesions ABC, UBC, chondromyxoid fibroma, chondroblastoma    
Stage 3 Aggressive lesions giant cell tumor of bone  
 
Presentation
  • Symptoms
    • asymptomatic, discovered incidentally on radiographs 
      • usually true for enchondromas in long bones and foot
    • pathologic fracture
      • often seen with enchondromas in the hand  
    • pain
      • pain is uncommon
      • when a patient presents with an enchondroma and pain in the adjacent joint, the cause of pain is often unrelated to the tumor
      • unlike enchondroma, most chondrosarcomas have non-mechanical pain (rest pain and nocturnal pain)
  • Physical exam
    • shortening and angular deformities    
      • enchondromas may disrupt the growth plate
    • multiple bluish angiomas in Maffucci's syndrome  
Imaging
  • Radiographs
    • recommended views
      • skeletal survey if polyostotic disease is suspected
    • findings
      • well defined, lucent, central medullary lesions that calcify over time 
      • 1 to 10cm in size
        • metaphyseal location when they first appear
        • appear more diaphyseal as the long bone grows
      • "pop-corn" stippling, arcs, whorls, rings 
      • minimal endosteal erosion (<50% width of cortex)
      • cortical expansion and thinning may be present in hands, feet  
        • but not in long tubular bones (femur, tibia)
      • may have purely lytic appearance (especially in hand) 
      • Ollier's disease
        • enchondromas markedly expand the bone
        • bones are dysplastic, with shortening and bowing  
      • Maffucci's syndrome  
        • enchondromas markedly expand the bone  
        • angiomas are visible as calcified phleboliths  
      • unlike enchondromas, chondrosarcomas display
        • cortical thickening and destruction
        • endosteal erosions and scalloping >50% of the width of the cortex
        • are larger (>5cm)
  • Bone scan 
    • indications
      • to help differentiate chondrosarcoma from enchondroma
      • to identify polyostotic disease
      • rarely adds useful information
        • only 20% have more uptake than ASIS
        • most enchondromas are small, and easily identified as benign
    • findings  
      • increased uptake, but less than chondrosarcoma 
        • because of continued remodeling within the lesion
  • MRI 
    • indications
      • usually not necessary for diagnosis
      • identify size and intramedullary extent and soft tissue extension
      • differentiate from chondrosarcoma
    • findings  
      • lobular and bright on T2-weighted images  
      • no bone marrow edema or periosteal reaction
      • may show steak of cartilage or "sled runner tracks" 
      • medullary fill >90% suggests chondrosarcoma instead
Studies
  • Core needle-biopsy
    • from areas of bone scalloping or lysis
    • prone to sampling error due to tumor heterogeneity
      • chondrosarcomas may contain areas of benign hyaline cartilage
    • often impossible to differentiate from low-grade chondrosarcoma
  • Histology
    • gross appearance
      • blue gray, lobulated hyaline cartilage, with scattered calcifications
    • microscopic
      • solitary lesions in long bones
        • hypocellular with bland, mature hyaline cartilage (blue balls of cartilage) separated by normal marrow     
          • differentiates from chondrosarcoma
        • endochondral ossification encases cartilage with lamellar bone
        • abundant extracellular matrix with no myxoid component
      • solitary lesions in small tubular bones and fibula, Ollier's and Maffucci's syndromes
        • hypercellular, with mild chondrocytic atypia
      • characteristics of chondrocytes
        • small, bland chondroid cells in lacunar spaces 
        • uniform staining nuclei
        • no pleomorphism, mitoses, anaplasia, hyperchromasia or multinucleate cells
    • unlike enchondromas, chondrosarcomas display
      • hypercellularity, with plump nuclei
      • multiple binucleate cells
      • giant cells with clumps of chromatin
Differential
  • Bone infarct
    • "smoke up the chimney" radiographic appearance  
    • MRI does not give high T2 signal
      • enchondromas have high T2 signal because of high water content of cartilage
  • Chondrosarcoma
    • worsening pain
    • large size
    • deep endosteal scalloping >2/3 of cortical thickness
    • periosteal reaction, cortical breakthrough
    • rare in hands, feet, more common in pelvis, scapula, ribs
      • the converse is true for enchondroma
    • radiographic appearance differentiating low grade chondrosarcoma from enchondroma (see below)
Treatment
  • Nonoperative
    • observation
      • indications
        • treatment for vast majority of asymptomatic enchondromas  
      • follow up
        • serial radiographs at 6 months and 12 months to confirm radiographic stability
        • long term follow-up for patients with multiple enchondroma syndromes
  • Operative
    • intralesional curettage and bone grafting  
      • indications
        • lesion that shows any change on serial xrays
        • radiographs suspicious for low-grade chondrosarcoma
        • large lesions at risk for recurrent fracture
      • outcomes
        • local recurrence is unusual
    • immobilization, followed by currettage and bone grafting
      • indications
        • pathologic fracture in small tubular bones (hand lesions) because repeated fractures will usually occur
      • technique
        • immobilize until fracture union, followed by currettage and grafting
Complications
  • Malignant transformation
    • risk of transformation of enchondroma to chondrosarcoma
      • solitary enchondroma 
        • risk of malignant transformation is 1%
      • Ollier's disease                    
        • risk of malignant transformation is 25-30%
      • Maffucci's syndrome 
        • risk of malignant transformation is 25-30%, but up to 100% risk of other visceral and CNS malignancies as well
Image Bank
Case
Location
Xray
CT
Bone scan
MRI
MRI
Histo(1)
Case A prox. humerus
 
 
   
Case B prox. humerus
 
 
 
Case C prox. fibula
 
 
 
Case D prox. humerus
 
 
 
Case E hand
 
 
 
Case F distal femur
 
 
 
Case G prox. humerus
 
 
 
Case H Olliers - hand
 
 
 
Case I Maffucci - hand
 
 
 
Case J Olliers - humerus
 
 
 
Case K Olliers - forearm          
(1) - histology does not always correspond to case


 

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