Chondrosarcoma
Overview
- Malignant cartilage-producing tumor
- Second most common primary malignant bone tumor in adults (after myeloma)
- Can be primary or secondary from Osteochondroma or Enchondroma
Epidemiology
- Age: Typically >40 years
- Male predominance
- Secondary types often occur in younger adults with Multiple hereditary exostoses or enchondromatosis
Locations
- Pelvis, proximal femur, scapula, ribs
- Long bones: metaphyseal-diaphyseal regions
- Can occur in flat bones and small bones (hands/feet in Maffucci)
Histology
- Lobules of hyaline cartilage with variable cellularity
- Binucleated chondrocytes may be present
- Grading (1–3) based on mitotic activity, cellularity, nuclear atypia
Subtypes
| Subtype | Notes |
|---|---|
| Conventional | Most common |
| Clear cell | Epiphyseal, younger adults, low-grade |
| Dedifferentiated | High-grade, aggressive |
| Mesenchymal | Rare, small round cell component |
| Secondary | From Osteochondroma or Enchondroma; transformation risk increases with size and pain |
Imaging Features
X-ray / CT
- Lytic lesion with chondroid matrix:
- Rings and arcs
- Stippled or flocculent calcification - Endosteal scalloping (especially in long-standing enchondroma)
- Cortical destruction or soft tissue mass suggests malignancy
- >2 cm cartilage cap in osteochondroma = suspicious for secondary transformation
MRI
- T1: Low to intermediate signal
- T2: Very high signal (cartilage is water-rich)
- Post-contrast: Heterogeneous enhancement; helps define extent and soft tissue involvement
- Look for:
- Endosteal scalloping > 2/3 cortex
- Cortical breach or soft tissue mass
- Intramedullary size >5 cm favors malignancy
Differential Diagnosis
| Diagnosis | Key Differences |
|---|---|
| Enchondroma | Smaller, asymptomatic, no cortical breach or mass |
| Osteochondroma | Benign if cartilage cap < 1.5–2 cm (adults) |
| Fibrous dysplasia | Ground-glass matrix, no cartilage calcification |
| Low-grade Osteosarcoma | Osteoid matrix, more periosteal reaction |
| Metastasis / Myeloma | No chondroid matrix; age-dependent |
Management
- Surgical resection with wide margins is mainstay
- Chemotherapy and radiotherapy are generally ineffective (except mesenchymal subtype)
Prognosis
- Depends on grade, location, and subtype
- Low-grade: Good prognosis with adequate resection
- High-grade: Risk of recurrence and metastasis
- Dedifferentiated and mesenchymal: Poorer prognosis
Exam tips
- Middle-aged patient + pelvic/long bone lytic lesion + rings and arcs = chondrosarcoma
- Key differentiator from Enchondroma:
- Pain, soft tissue mass, cortical destruction, or cap >2 cm
- Watch out for secondary transformation in known Osteochondroma
Real-Life Reporting Tips
- Report:
- Matrix type (chondroid vs osteoid)
- Presence/absence of soft tissue mass
- Cortical breakthrough or endosteal scalloping
- Cap thickness (if osteochondroma)
- Suggest malignancy if:
- Lesion is painful, enlarging
- Intramedullary size >5 cm, aggressive features
- Cartilage cap >2 cm in adults
