[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Bones, joints and soft tissue](https://durgical.com/en/general-pathology/areas/bone-soft/) › Benign cartilage tumours: osteochondroma and enchondroma

# 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.

Updated Nov 12, 2026

## Key points

- Osteochondroma: most common benign bone tumour; stalk continuous with the host medulla and cortex, capped by cartilage; adolescents, around the knee.
- EXT1/EXT2 (heparan sulfate synthesis) loss; hereditary multiple osteochondromas is autosomal dominant with a higher risk of chondrosarcoma.
- Enchondroma: hyaline cartilage nodule in the medulla of hand and foot bones; IDH1/IDH2 mutations.
- Ollier disease (many enchondromas) and Maffucci syndrome (enchondromas plus haemangiomas) carry a high risk of chondrosarcoma; Maffucci also of other cancers.
- Chondroblastoma: epiphysis of long bones in teenagers; chicken-wire calcification; H3F3B (H3.3 K36M) mutation.
- Growth of a cartilage cap after skeletal maturity or new pain suggests malignant change.

## 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.

## Memory aid

Osteochondroma flees the joint on a stalk; enchondroma hides inside the hand; chondroblastoma camps at the epiphysis.

## 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.

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## Elsewhere in DurgiPedia

- [Cartilage: hyaline, elastic, fibrocartilage](https://durgical.com/en/histology/cartilage-hyaline-elastic-fibrocartilage/)
- [Ossification, growth plate and bone remodeling](https://durgical.com/en/histology/ossification-growth-plate-and-bone-remodeling/)

## Connections

## Related 4

- [Benign vs malignant tumours: the comparison table](https://durgical.com/en/general-pathology/benign-vs-malignant-tumours-the-comparison-table/)
- [Chondrosarcoma](https://durgical.com/en/general-pathology/chondrosarcoma/)
- [Bone tumours at a glance](https://durgical.com/en/general-pathology/bone-tumours-at-a-glance/)
- [Benign vascular tumours](https://durgical.com/en/general-pathology/benign-vascular-tumours/)

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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](https://medlineplus.gov/genetics/condition/hereditary-multiple-osteochondromas/) (MedlinePlus, US National Library of Medicine, 2025); [Ollier disease: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/ollier-disease/) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/benign-cartilage-tumours-osteochondroma-and-enchondroma/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/benign-cartilage-tumours-osteochondroma-and-enchondroma/