High Yield Topics

Enchondroma

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Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.
Title: 5-Minute Orthopaedic Consult, 2nd Edition
> Table of Contents > Enchondroma

Enchondroma
Frank J. Frassica MD
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

    • P.117


  • 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 (e.g., those in Table 1).
  • 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.
Table 1 Possible Causes of Pain
Enchondroma Site Associated Conditions
Proximal humerus Rotator cuff tendinitis, rotator cuff tear, glenohumeral arthritis
Proximal femur Trochanteric bursitis, hip arthritis
Distal femur Patellofemoral syndrome, knee arthritis
Surgery
  • 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 (e.g., those in Table 1).
  • 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 (1).
    • 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 (1).
    • Malignant brain tumors and liver and pancreatic carcinomas also may develop.
References
1. Dorfman HD, Czerniak B. Benign cartilage lesions. In: Bone Tumors, St. Louis: Mosby, 1998:253–352.
Additional Reading
Biermann JS. Musculoskeletal neoplasms. In: Richards BS, ed. Orthopaedic Knowledge Update: Pediatrics. Rosemont, IL: American Academy of Orthopaedic Surgeons, 1996:55–64.
Cole WG. Genetic aspects of orthopaedic conditions. In: Morrissy RT, Weinstein SL, eds. Lovell and Winter’s Pediatric Orthopaedics, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006:145–165.
Gitelis S, Soorapanth C. Benign chondroid tumors. In: Menendez LR, ed. Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL: American Academy of Orthopaedic Surgeons, 2002:103–112.
Mackenzie WG, Gabos PG. Localized disorders of bone and soft tissue. In: Morrissy RT, Weinstein SL, eds. Lovell and Winter’s Pediatric Orthopaedics, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006:315–356.
McCarthy EF, Frassica FJ. Primary bone tumors. In: Pathology of Bone and Joint Disorders: With Clinical and Radiographic Correlation. Philadelphia: WB Saunders, 1998:195–275.
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.

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