CMF

Bone

Benign

Male

Cartilage

• Rare, <1% of primary bone tumours
• Peak incidence 2nd-3rd decades
• Slight male predominance
• Often misdiagnosed due to rarity and histological complexity

• Pain and swelling, often mild and chronic
• May be asymptomatic - incidental finding
• Pathological fracture rare
• Soft tissue extension uncommon

• Metaphysis of long bones
• Proximal tibia most common
• Femur, fibula, foot bones
• Flat bones (pelvis, ribs) in older patients

• Plain radiograph: Eccentric lytic lesion with lobulated scalloped margins. Metaphyseal region. Geographic Bone destruction with sclerotic rim. May cause cortical expansion.
• MRI: may show secondaty ABC, T1 low signal, T2 intermediate to high signal

• Lobular architecture with myxoid/chondroid matrix
• Cellular periphery, hypocellular centre of lobules
• Stellate and spindle cells
• GRM1 gene fusions (EWSR1-GRM1) detected in majority

• GRM1 rearrangements (EWSR1-GRM1 most common)
• Unique molecular profile distinct from other cartilaginous tumours
• No IDH mutations

• Curettage and Bone grafting - standard treatment
• En bloc resection for expendable bones or recurrent lesions
• Local recurrence rate 15-25%

• Benign with low recurrence rate
• Malignant transformation extremely rare
• Excellent long-term outcome after adequate surgery

• Benign cartilagenous bone tumour in young adults
• Metaphyseal location common
• EWSR1-GRM1 fusion gene is characteristic and diagnostically useful
• Curettage with adjuvants preferred to reduce recurrence
• High rate of local recurrence; long term follow-up recommended

No blood tests required

• Plain radiograph
• CT - characterises lesion and cortical integrity
• MRI

Biopsy if imaging atypical or diagnostic uncertainty

No staging required