Tumor biology and incidence
- Generally a benign latent cartilage lesion except in phalanges where pain or fracture may be presenting features
- Probably arises from a "rest" of physeal cartilage that migrates to metaphysis
- Considered benign active if painful or if there is cortical erosion
- When active, lesion must be differentiated from low-grade chondrosarcoma on analysis of clinical, radiographic, and pathologic features.
- Differentiation can prove to be difficult in many cases.
- Common benign bone tumor, with active lesions and incidental findings accounting for about 15% of all benign bone tumors
- Incidence is probably higher, as most enchondromas are asymptomatic
Most commonly present from ages 15-40 years
M:F = 1:1
- Lesions in long bones generally asymptomatic and discovered incidentally
- Often discovered as the result of injury or non-neoplastic orthopaedic complaints (chondromalacia or rotator cuff tendonitis)
- Active lesions in long bones are rare and are defined by pain
- Lesions in the hand or, less commonly, the foot more commonly active
- Erode cortical bone with resulting pain, bony mass, or pathologic fracture
- Often no findings, but may be local tenderness at site of an active lesion
- Expansile lesions in the hand may cause a palpable bony mass
- History, physical examination, and plain x-rays must be considered together and are the most valuable modalities for identification of an enchondroma.
- Worrisome features for chondrosarcoma
- Endosteal scalloping/ erosion in a long bone lesion
- Permeative lucency within or surrounding an otherwise typical long bone enchondroma
- In long bones, enchondroma occurs in meta-diaphysis; most common in femur, humerus
- In short, tubular bones of hand, enchondromas are commonly diaphyseal (proximal phalanx > metacarpals> mid phalanx> distal phalanx)
- Variable: 3-5 cm
- Smaller in hands or feet.
Tumor effect on bone
- Generally little endosteal erosion seen except in hands
- Minor degree of endosteal scalloping secondary to a lobular growth pattern
- Hand lesions may be quite erosive
- May have a very aggressive x-ray appearance and still remain benign
Bone response to tumor
Geographic pattern but little endosteal response
- Matrix commonly described as "comma-shaped," "popcorn," or "stippled" calcification
- Calcification more prominent in long bones; uncommon in hands and feet
- Often radiolucent in the hands
- May see erosion and expansion of the cortex of the hand or foot bones
- Usually no cortical erosion in long bones (unless pathologic fracture)
Soft tissue mass
- No soft tissue mass
- Lesion may erode through cortex with associated soft tissue mass, though rare
- Called "enchondroma protuberans"; observed mainly in the hand
- Benign latent lesions often show modest increased uptake on bone scan
- Enchondroma may be quite "hot" on occasion
- Not a good test for differentiating benign and malignant cartilage tumors
- Multiple lesions on bone scan suggest Ollier's disease
- Evaluation of calcifications
- Evaluation of endosteal scalloping/erosion and lucency within the lesion in differentiating chondrosarcoma from enchondroma
- Calcification shows absence of signal intensity on both T1 and T2 sequences
- Hyaline (not calcified) cartilage is bright on T2 weighted imaging due to high water content of cartilaginous matrix
- MRI not definitive for differentiating benign and malignant lesions unless it demonstrates a soft tissue mass or other aggressive features
- Medullary bone infarct (especially in long bones)
- Infarcts have "smoke rising from a chimney" appearance; can be difficult to differentiate from enchondroma
- Giant cell tumor
- May affect metacarpals, rarely phalanges in hand
- Fibrous dysplasia
- In long bonesm minimally calcified enchondroma may resemble fibrous dysplasia
- Unicameral bone cyst, in long bones
- Chondrosarcoma, in long bones
- Cortical erosion, permeative changesm and lytic regions seen in malignant lesions
- Growth of lesion is rare after skelatal maturity
- Malignant transformation can occur in 1% of solitary lesions
- Patients with Ollier's disease (multiple enchodromas) have significant risk of malignant transformation – up to 30%
- Patients with Maffucci's syndrome (multiple enchondromas and associated soft tissue lesions, most commonly hemangiomas) reported to have 100% risk of malignant transformation
- Gross: Well circumscribed lobules of cartilage.
- Microscopic: Nodules of hyaline cartilage containing chondrocytes with small, condensed nuclei
- Low cellularity, minimal nuclear atypiam and absence of binucleate cells distinguishes enchondroma from low-grade chondrosarcoma
- Differentiation from low-grade chondrosarcoma may be difficult; consider the clinical and radiologic data with histological appearance when making diagnosis
- More cellularity and nuclear atypia may be observed in lesions located in hand or foot.
Diagnosis and treatment
- In latent lesions, diagnosis confirmed by initial plain x-ray and follow up x-rays showing lack of progression
- Avoid biopsying lesions; pathologic diagnosis may be difficult unless:
- The lesion changes over time
- There is persistent pain without other clinically evident cause
- There are worrisome x-ray findings of endosteal erosion, permeative lysis.
- If lesion appears benign, observation is appropriate
- Wait 3 months for repeat x-ray.
- If no changes, repeat in 6 months and 1 year
- If lesion is symptomatic, curettage and bone graft usually curative
- Most commonly necessary in the hand or, less frequently, the toes.
- Pathologic fracture, especially in the hand and, less frequently, the foot
- Malignant transformation to secondary chondrosarcoma rare in solitary lesions
Oncology and Basic Science. Ed: Timothy A. Damron. Orthopedic Surgery Essentials Series, 576pp, Philadelphia, PA, Lippincott Williams & Wilkins, 2007.
Orthopaedic Knowledge Update: Musculoskeletal Tumors 2. Herbert S. Schwartz, MD, Editor. American Academy of Orthopaedic Surgeons, Rosemont Il, 2007
Flemming DJ, Murphey MD: Enchondroma and Chondrosarcoma. Semin Musculo Radiol 2000;4:59-71.