Benign cartilage tumours: osteochondroma and enchondroma
- Lesion
The commonest benign bone tumours make cartilage: a bony stalk with a cartilage cap, or a cartilage nodule inside the bone.
What it is
Cartilage-forming tumours are the commonest benign bone tumours. Osteochondroma is a bony outgrowth capped by cartilage that grows from the metaphysis away from the joint, driven by loss of EXT1 or EXT2; multiple lesions occur in hereditary multiple osteochondromas. Enchondroma is a nodule of hyaline cartilage in the medullary cavity, usually of the small bones of the hands and feet, linked to IDH1 or IDH2 mutations; many enchondromas define Ollier disease, and with soft-tissue haemangiomas, Maffucci syndrome. Chondroblastoma is an epiphyseal tumour of adolescents, and chondromyxoid fibroma is a rare lobulated metaphyseal tumour.
Structure
- Osteochondroma: mushroom-shaped or sessile lesion; the cortex and marrow flow into the stalk; cartilage cap looks like a disorganized growth plate and ossifies at its base.
- Enchondroma: well-circumscribed lobules of bland hyaline cartilage with small chondrocytes in lacunae, often calcified ('rings and arcs' on X-ray).
- Chondroblastoma: sheets of round to polygonal cells with grooved nuclei, osteoclast-type giant cells and fine pericellular calcification ('chicken wire').
- Chondromyxoid fibroma: lobules with stellate cells in myxoid matrix, more cellular at the periphery.
Step by step
- In growing bone, a misplaced group of growth-plate chondrocytes loses both copies of EXT1 or EXT2.
- Abnormal heparan sulfate changes Indian hedgehog signaling, and the cells grow out laterally from the metaphysis.
- The outgrowth ossifies from its base, forming a stalk continuous with the host bone.
- Growth stops when the skeleton matures; renewed growth suggests chondrosarcoma.
- Enchondromas arise from IDH1 or IDH2 mutations that produce the oncometabolite 2-hydroxyglutarate and alter epigenetic control of chondrocytes.
Benign cartilage tumours compared
| Tumour | Age | Location | Key features |
|---|---|---|---|
| Osteochondroma | Adolescents | Metaphysis of long bones (around the knee) | Bony stalk with a cartilage cap pointing away from the joint; EXT1/EXT2 |
| Enchondroma | Young and middle-aged adults | Medulla of hand and foot bones | Lobules of bland hyaline cartilage; IDH1/IDH2 |
| Chondroblastoma | Teenagers | Epiphysis (femur, tibia, humerus) | Grooved cells, giant cells, chicken-wire calcification |
| Chondromyxoid fibroma | Young adults | Metaphysis of tibia, pelvis | Lobulated myxoid tumour with stellate cells |
Clinical notes
- Osteochondromas are often found as a painless hard lump; they can irritate tendons, nerves or vessels or fracture at the stalk.
- Enchondromas are usually silent until a fracture of a finger.
- Patients with Ollier disease or Maffucci syndrome need follow-up for malignant transformation.
Test yourself
Think of the answer, then tap the question to see it.
Which genes are lost in osteochondroma?
EXT1 or EXT2, which make enzymes for heparan sulfate synthesis.
What defines Maffucci syndrome?
Multiple enchondromas plus soft-tissue haemangiomas.
Where does chondroblastoma arise?
In the epiphysis of long bones, usually in teenagers.
What sign suggests malignant change in an osteochondroma?
New pain or growth of the cartilage cap after the skeleton has matured.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Hereditary multiple osteochondromas: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2025); Ollier disease: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.