Introduction
This note covers four benign bone tumours of the syllabus: chondroma (enchondroma), osteochondroma, haemangioma of bone and giant cell tumour (osteoclastoma). For the exam, know each tumour's typical site and age, its radiographic signature, the features that suggest malignancy, and the usual management. Osteoma and osteoid-osteoma are covered in the previous topic.
Chondroma (enchondroma)
A chondroma is a benign tumour of mature hyaline cartilage arising inside the medullary cavity of bone. It is usually a solitary, central lesion and is often found by chance on an X-ray taken for another reason. A chondroma that develops inside the bone is an enchondroma; one that develops outside the bone is an ecchondroma.
- Site: small bones of the hands and feet (phalanges, metacarpals) are most typical; also proximal humerus, femur and tibia.
- Age: mainly young adults; the lesion stops growing once skeletal maturity is reached.
- Radiograph: well-defined lytic (radiolucent) lesion in the medulla of homogeneous, cellular or lacunar structure, with or without granular calcifications, sometimes with stippled or ring-and-arc calcification of the cartilage matrix; in long bones there may be mild endosteal scalloping but no periosteal reaction unless fractured.
Lateral X-ray of a phalanx: radiolucent shadow of homogeneous, cellular or lacunar structure, with or without granular calcifications. It develops inside the bone, so this is an enchondroma.
AP X-ray of the hand showing the same picture, but the tumour develops outside the bone: an ecchondroma. Diagnosis: chondroma.
- Clinical: usually asymptomatic; pain or a pathological fracture prompts investigation, especially in the hand where a fracture may be the first sign.
- Malignant potential: a solitary enchondroma rarely becomes a chondrosarcoma, but the risk is much higher in multiple enchondromatosis (Ollier disease) and Maffucci syndrome, and in large central lesions of the femur, humerus or pelvis.
- Management: asymptomatic lesions are observed with serial imaging; symptomatic or fracture-prone lesions are treated by curettage with bone grafting or cementing.