Chondromyxoid Fibroma
Synonyms: CMF
EWSR1-GRM1 fusion gene is characteristic and diagnostically useful
Quick Facts
Behaviour
Benign
Category
Bone
Synonyms
CMF
Category
Bone
Behaviour
Benign
Gender
Male
Tissue of Origin
Cartilage
Epidemiology
- Rare, <1% of primary Bone tumours
- Peak incidence 2nd–3rd decades
- Slight Male predominance
- Often misdiagnosed due to rarity and histological complexity
Clinical Features
- Pain and swelling, often mild and chronic
- May be asymptomatic - incidental finding
- Pathological fracture rare
- Soft tissue extension uncommon
Location
- Metaphysis of long bones
- Proximal tibia most common
- Femur, fibula, foot bones
- Flat bones (pelvis, ribs) in older patients
Imaging
- Eccentric lytic lesion with lobulated scalloped margins
- Geographic Bone destruction with sclerotic rim
- May cause cortical expansion
- No mineralisation (unlike enchondroma/chondrosarcoma)
Pathology
- Lobular architecture with myxoid/chondroid matrix
- Cellular periphery, hypocellular centre of lobules
- Stellate and spindle cells
- GRM1 gene fusions (EWSR1-GRM1) detected in majority
Genetics
- GRM1 rearrangements (EWSR1-GRM1 most common)
- Unique molecular profile distinct from other cartilaginous tumours
- No IDH mutations
Treatment
- Curettage and Bone grafting - standard treatment
- En bloc resection for expendable bones or recurrent lesions
- Local recurrence rate 15–25%
Prognosis
- Benign with Low recurrence rate
- Malignant transformation extremely rare
- Excellent long-term outcome after adequate surgery
Key Points
- EWSR1-GRM1 fusion gene is characteristic and diagnostically useful
- No IDH mutations - helpful to distinguish from Low-grade chondrosarcoma
- Histological misdiagnosis as chondrosarcoma not uncommon due to cellularity
- Curettage with adjuvants preferred to reduce recurrence
Workup - Blood Tests
No blood tests required
Workup - Local Imaging
- Plain radiograph
- CT - characterises lesion and cortical integrity
- MRI
Workup - Biopsy
- Biopsy if imaging atypical or diagnostic uncertainty
- Histology: nodular myxoid and chondroid areas with peripheral fibrosis
Workup - Staging
No staging required
Follow-up Summary
- 1
Post-op visit at 6 weeks
- 2
Year 1–2
6-monthly clinical review + plain X-ray
- 3
Year 3–5
Annual review with X-ray; discharge if no recurrence at 5 years
- 4
No CT/MRI routinely required unless recurrence suspected on plain films
- 5
No systemic metastatic risk - no chest imaging required
- 6
High misdiagnosis rate
ensure final histology confirmed by sarcoma MDT before Follow-up plan
Medical disclaimer
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