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Enchondroma


  • General considerations
    • Benign cartilaginous tumor
    • Develops in the medullary cavity
    • Usually solitary, although they can occur as multiple lesions in syndromes to be discussed
    • Arise from ectopic rests of hyaline cartilage
    • Occur mostly in 2nd to 3rd decade
    • Most common site is small bones of the hands and feet
      • Most occur in the proximal phalanx
    • Most common tumor of the hand
      • Also occur in the humerus, femur, tibia and ribs
    • In long bones, their calcification is similar to an intramedullary bone infarct
      • Bone infarcts tend to have a well-circumscribed, sclerotic margin
    • May fracture or, rarely, undergo malignant transformation
      • On CT, lucent regions in an otherwise dense enchondroma suggest malignancy
    • Rapid growth of lesion or pain not related to a pathologic fracture may  suggest malignant transformation
  • Clinical findings
    • Usually asymptomatic and found serendipitously
    • May be associated with pain and swelling which should raise suspicion of either a pathologic fracture or, less likely, malignant transformation
      • Malignant transformation almost never occurs in the hands and feet
  • Imaging findings
    • Conventional radiography is the study of first choice
    • Well-defined lytic and slightly expansile lesion (in small bones)
    • Usually have some internal calcification and endosteal thinning
      • Internal calcifications tend to resemble “rings and arcs” of cartilage calcification
    • MRI findings
      • Numerous internal foci with high-signal intensity on T2
      • Low to intermediate signal on T1
      • Lobulated in contour
    • Bone scan
      • Negative if uncomplicated enchondroma
  • Multiple enchondromas occur in Ollier's disease
    • Nonhereditary
    • Frequently unilateral
    • Enchondromas are frequently larger than with solitary enchondroma
    • May have limb shortening of affected limb
    • May have Madelung’s deformity of the wrist
    • Greater incidence of malignant transformation because there are more lesions present (25-50%)
  • Enchondromas associated with cavernous hemangiomas of soft tissues is called Maffucci’s Syndrome
    • Nonhereditary
    • Even more rare than Ollier’s disease
    • Multiple hemangiomas usually in extremities (digits)
    • Look for phleboliths in hemangioma
    • Growth disturbance of affected bones
    • Malignant transformation
      • Greater than solitary enchondroma, less than Ollier’s
      • Hemangioma may become sarcoma in 5% of cases

Enchondroma with pathologic fracture. Left: There is a non-displaced fracture through the base of the proximal phalanx of the 4th toe (white arrow). Right: A well-defined, slightly expansile, lytic lesion is seen in the proximal phalanx (white circle) through which the fracture has occurred.
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