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Images C_moved.jpg E - distal phalanx - xray - Parsons_moved.png C - fibula - xray - Parsons_moved.png D - prox humerus - xray - Parsons_moved.png foot.jpg b - prox humerus - xray - parsons.png
  • summary
    • Enchondromas are benign latent cartilaginous tumors composed of hyaline cartilage that typically occur in medullary cavity of the diaphysis or metaphysis. Patients typically present between the ages of 20-50 with an asymptomatic lesion, discovered incidentally on radiographs.
    • Diagnosis is made radiographically with the presence of a well-defined, lucent, central medullary lesion that is 1-10 cm, and often associated with "pop-corn" stippling, arcs, whorls, or rings.
    • Treatment is observation as most lesions are asymptomatic.
  • 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
    • Anatomic location
      • usually found in the medullary cavity of the diaphysis or metaphysis
      • the most common locations hand (60%) > feet
        • the most common primary bone tumor in the hand is the enchondroma
      • other locations include distal femur (20%) > proximal humerus (10%) > tibia
  • Etiology
    • Pathophysiology
      • invole IDH-1 & IDH-2 gene
      • enchondromas represent incomplete endochondral ossification
        • chondroblasts and fragments of epiphyseal cartilage escape from the physis, displace into the metaphysis and proliferate there
      • malignant transformation in <1% to chondrosarcoma
    • Associated conditions
      • 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
        • distinguished by soft-tissue angiomas
        • Marked expansion of lesion on radiographs, with angiomas are seen as small, round calcified phleboliths
        • increased risk of visceral malignancies (astrocytoma, GI malignancy)
          • overall risk of developing any malignancy up to 100%
  • 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
        • more likely in hand and feet secondary to pathologic fractures
        • differentiates from chondrosarcomas (non-mechanical pain rest pain and nocturnal pain)
    • Physical exam
      • shortening and angular deformities (in inherited diseases)
        • enchondromas may disrupt the growth plate
      • multiple bluish angiomas in Maffucci's syndrome
  • Imaging
    • Radiographs
      • usually diagnostic
      • 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 (inherited diseases)
          • may have purely lytic appearance
      • skeletal survey if polycystic disease is suspected
        • Ollier's disease
          • bones are dysplastic, with shortening and bowing
        • Maffucci's syndrome
          • angiomas are visible as calcified phleboliths
      • unlike chondrosarcomas 
        • cortical thickening and destruction
        • endosteal erosions and scalloping >50% of the width of the cortex
        • are larger (>5cm)
    • Bone scan
      • indications
        • help differentiate from chondrosarcoma
        • 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 due to continued remodeling within lesion
          • less uptake than chondrosarcoma
    • MRI
      • lobule and bright on T2 without marrow edema or periosteal reaction
      • indications
        • usually not necessary for diagnosis
        • identify size and intramedullary extent and soft tissue extension
        • differentiate from chondrosarcoma and bony infarcts
      • 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
        • mature hyaline cartilage lobules separated by normal marrow
        • 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
          • 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 chondrosarcomas
        • hypercellularity, with plump nuclei
        • multiple binucleate cells
        • giant cells with clumps of chromatin
  • Differential
    • Bone infarct
      • "smoke up the chimney" radiographic appearance
      • MRI has low T2 signal
    • Chondrosarcoma
      • deep endosteal scalloping >2/3 of cortical thickness
      • more common in pelvis, scapula, ribs
  • Treatment
    • Nonoperative
      • observation
        • 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
          • symptomatic lesions
          • pathologic fractures 
            • immediate curettage and grafting are now favored
            • no difference in outcomes between delayed and immediate curettage and grafting
          • radiographs suspicious for low-grade chondrosarcoma
          • large lesions at risk for recurrent fracture
        • outcomes 
          • local recurrence is unusual
  • 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
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