Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Enchondroma

Basics
Description
  • A common benign lesion of mature hyaline cartilage in the medullary canal of the metaphysis or metadiaphysis of bone
  • Commonly involves the short tubular bones (usually proximal phalanx) of adult hands and feet:
    • Also may involve the distal femur, proximal humerus, and tibia
    • Rare in the spine and pelvis
    • Does not form in bones that develop by membranous ossification
  • Nongrowing lesion
  • Small peripheral cartilage tumors tend to be benign, whereas large axial tumors have the greatest risk of malignancy.
Epidemiology
Incidence
  • One of the most common benign bone tumors
  • Most common bone tumor of the hand
  • Most common destructive bone lesion in hand
Prevalence
  • Found in all age groups but more commonly recognized in adults
  • The Male:Female ratio is equal.
Etiology
  • May result from epiphyseal growth cartilage that does not remodel and persists in the metaphysis, or may be the persistence of the original cartilage anlage
  • Cartilage stops growing in adulthood.
Associated Conditions
  • Enchondroma protuberans: Eccentric enchondroma may cause bulging of the cortex.
  • Enchondromatosis (Ollier disease): Multiple enchondromas:
    • Widespread involvement of the skeletal system by chondromas that occur principally in the medullary cavity but also on the surface of the bone
    • Typically occurs in a unilateral distribution
    • May involve any bone
    • Occurrence in multiple siblings has been documented, but no genetic basis has been found.
  • Maffucci syndrome: Multiple enchondromas with soft-tissue hemangiomas
Diagnosis
Signs and Symptoms
  • General features:
    • Most lesions are asymptomatic.
      • Enchondromas of the long bones do not cause pain.
      • Patients with intramedullary cartilage lesions and pain should be evaluated carefully for another source of pain, possibly a chondrosarcoma.
    • Pain sometimes is present in patients with enchondromas in the hand from pathologic fractures.
    • If lesions occur in the hand, some enlargement of the digit may be noted if the cortex is expanded.
    • The lesion usually is diagnosed incidentally on a routine radiograph or bone scan and frequently is hot on a bone scan.
    • Rarely, a chondrosarcoma may develop in a pre-existing enchondroma (typically in the long bones).
  • Enchondromatosis:
    • Usually recognized clinically by 10 years of age because of the development of palpable masses, unilateral shortening of an extremity, or angular deformity
    • Most cases are bilateral, but involvement usually predominates on 1 side.
      • Within an extremity, the lesions may be asymmetric (i.e., affecting the radial side more than the ulnar side, or vice versa).
    • Affected bones are shortened or deformed by epiphyseal involvement.
    • The disease regresses after puberty.
  • Maffucci syndrome:
    • Vascular phleboliths are apparent in the associated soft-tissue hemangiomas.
Physical Exam
Palpate the bone for tenderness and a soft-tissue mass.
 
Tests
Imaging
  • Children: Plain radiographs in 2 planes and a bone scan should be obtained to evaluate for other lesions.
  • Radiography:
    • Serial radiographs taken every 3-6 months or review of old radiographs can help determine whether the lesion is inactive.
    • Well-defined, solitary, lytic lesions occur in the central portions of the metaphysis or metadiaphysis, with occasional endosteal scalloping and variable intralesional calcifications.
    • The calcification pattern is described as rings and stipple, popcornlike, and punctate.
    • In small tubular bones (e.g., the hand), the entire shaft usually is involved.
    • The cortex usually is intact, but it may be expanded mildly (by lack of remodeling in the metaphysis, not by expansion of the bone by tumor).
      • It often is radiolucent in children (may look like a unicameral bone cyst).
    • As patients age, the normally radiolucent cartilage begins to ossify and calcify, and ring-and-stipple calcifications are observed.
    • Occasionally, the mineralization is so dense that the lesion may suggest a bone infarct.
    • No periosteal reaction occurs.
    • Enchondromatosis:
      • Radiolucent areas of cartilage are seen in the metaphysis, with irregular calcification in a longitudinal or streaking pattern extending from the physis.
      • The cortices are expanded from within, inhibiting normal metaphyseal remodeling.
      • Affected bones cannot tubulate, so ends have a clubbed appearance.
      • The chondroma may be intracortical, subcortical, or in the epiphysis.
      • The tendency is to spare the epiphysis and diaphysis, but in severe cases, the entire bone may be involved.
  • MRI:
    • Well-circumscribed lobular lesion is bright on T2-weighted images.
    • Low signal intensity on T1-weighted images
  • Bone scanning:
    • Enchondromas take up radionuclide tracer and may be hot on a bone scan.
    • Positive bone scans should be interpreted cautiously because they do not, by themselves, indicate malignant change.
    • Although they do not grow, enchondromas are constantly remodeling.
    • Increased uptake and activity are not indications of malignant degeneration unless the lesion had less uptake on a previous scan.
    • Initial scans are used for baselines if any symptoms change.
Pathological Findings
  • Microscopic features:
    • Nests of cartilage cells without atypia are separated by normal marrow.
    • Foci of calcification usually are present.
    • A thin layer of lamellar cartilage may be observed.
    • Negative Ki-67 stain is noted.
    • Evidence of invasive infiltration of bone marrow suggests chondrosarcoma.
    • Low magnification: Hypocellular lesions with a blue-gray aura and inconspicuous nuclei.
    • High magnification: Lesions have uniform nuclei (small, regular, darkly stained), and binucleated cells are rare.
  • Hand lesions:
    • May be hypercellular
    • May have slight myxoid change
    • Nuclei may show atypical features.
    • Double nucleated cells are common.
Differential Diagnosis
  • Radiographic features:
    • Bone infarct
    • Chondrosarcoma
  • Benign versus malignant lesions:
    • Distinguishing a benign latent enchondroma and an active enchondroma or low-grade chondrosarcoma is a common and difficult clinical problem.
    • Because the histologic characteristics of an enchondroma overlap those of a low-grade chondrosarcoma, biopsy often is not helpful.
    • The correct diagnosis depends on observing and correlating clinical and radiographic features of the lesion.
      • Is the lesion growing?
      • Is the lesion painful?
  • Enchondroma:
    • Painless condition
    • Lack of growth
    • Bone scan variability
    • Uniform matrix calcification
    • Lack of endosteal erosion
    • Uniform small bland cells
    • Low cellularity
  • Low-grade chondrosarcoma:
    • Painful condition
    • Slow-growing lesion
    • Bone scan variability
    • Presence of lucent regions
    • Endosteal erosion
    • Mild cellular atypia
    • Moderate to high cellularity
    • Ki-67-positive status
Treatment
General Measures
  • Enchondromas do not cause pain, so other causes need to be sought.
  • Serial radiographs are obtained to ensure that the cartilage lesion is not growing.
    • Enchondromas show no changes except for increased mineralization.
    • Chondrosarcomas show:
      • Cortical erosions
      • Cortical thickening
      • Cortical destruction
  • Activity modification is not necessary regardless of the size of the enchondroma.
  • Patients with enchondromas of the hand often require curettage because of weakening of the bone.
  • If the bone has fractured, the fracture is allowed to heal before curettage and grafting.
  • General principles:
    • Surgery usually is not necessary for enchondromas of long bones.
    • Enchondromas of the hand, which often present with pathologic fracture, should be treated with curettage.
  • Hand lesions:
    • Make a small window in the lateral aspect of the phalanx for curettage and bone grafting.
      • Replace the cortical window.
    • Amputation may be necessary if finger function is compromised by the lesion.
  • Enchondromatosis:
    • Surgery may be necessary for angular deformities.
    • Osteotomies may be performed through the enchondroma.
    • Leg-length discrepancy may require epiphysiodesis or limb-lengthening procedures.
    • Hand lesions may require curettage and bone grafting because of their large size and interference with function.
Follow-up
  • Patients with long-bone enchondromas are followed with serial radiographs every 3-6 months for 1-2 years.
  • Patients are counseled to return for evaluation if the extremity becomes painful.
Disposition
Issues for Referral
  • Patients with enchondromas often have other sources of musculoskeletal pain.
  • Patients with enchondroma and musculoskeletal pain should be referred to an orthopaedic oncologist.
Complications
  • General complications: Malignant degeneration (look for pain and growth of lesion)
  • Enchondromatosis:
    • Of these patients, ~30% develop low-grade chondrosarcoma.
    • Usually occurs in patients in the 3rd and 4th decades of life
    • Look for changes on plain radiographs or MRI/CT scans.
  • Maffucci syndrome:
    • Almost 100% develop low-grade chondrosarcoma.
    • Malignant brain tumors and liver and pancreatic carcinomas also may develop.
Miscellaneous
Codes
ICD9-CM
756.4 Enchondroma, enchondromatosis, Maffucci syndrome
 
FAQ
Q: Do enchondromas cause pain?
A: In general, enchondromas do not cause pain. Often associated conditions are present, such as tendinitis, bursitis, or arthritis.
 
Q: Are plain radiographs enough to establish the diagnosis of enchondroma?
A: In general, plain radiographs are sufficient. If concern exists, a CT or MRI scan can be performed to ensure that no large cortical erosions, cortical destruction, or soft-tissue masses are present.
 
Q: Is there a substantial risk of a long-bone enchondroma converting into a chondrosarcoma?
A: The risk of an enchondroma transforming into a low- or high-grade chondrosarcoma is extremely low. Patients can and should be assured that the risk of malignancy is minimal.

1 comment to Enchondroma

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