CIM Case: De-differentiated Chondrosarcoma

Clinical Scenario

Patient: 62-year-old retired engineer Presentation: 3-month history of progressive right hip and groin pain following a minor fall, now requiring walking stick, night pain disturbing sleep Relevant history: Known enchondroma in proximal right femur monitored with X-rays for 10 years (stable until now), no previous surgery, no other medical conditions, non-smoker, independent mobility prior to current symptoms Examination findings:

• Slim man, looks well but uncomfortable
• Antalgic gait, using single-point stick
• Palpable fullness over anterolateral right proximal thigh
• Firm mass, fixed to deep structures
• No overlying skin changes
• Tenderness over greater trochanter region
• Hip ROM: flexion 90° (limited by pain), internal rotation 10° (limited), external rotation 20°
• No lymphadenopathy (inguinal)
• Neurovascularly intact distally
• No stigmata of Ollier disease or Maffucci syndrome

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Investigations Provided

Laboratory Results

Imaging

Image 1: AP and Lateral Radiographs of Right Hip/Proximal Femur

Radiological features:

• Large destructive lesion in proximal femur (intertrochanteric region)
• Biphasic appearance: areas of chondroid matrix (rings and arcs) AND areas of aggressive osteolysis
• Cortical destruction with breakthrough
• Periosteal reaction (Codman triangle, sunburst pattern)
• Soft tissue mass extending medially and laterally
• No pathological fracture yet but high risk
• Size approximately 10 x 8cm
• Extends from lesser trochanter to subtrochanteric region

Image 2: MRI of Right Proximal Femur

Findings:

• Large heterogeneous mass in proximal femur
• Bimorphic pattern: high T2 signal lobulated component (cartilage) adjacent to aggressive solid component
• Abrupt transition between components (diagnostic feature)
• Extensive medullary involvement
• Cortical destruction with extra-osseous extension
• Soft tissue mass 6cm in maximum dimension
• No skip lesions
• Neurovascular bundle displaced but appears intact
• Edema in adjacent muscles

Image 3: CT Chest (Staging)

Findings:

• Two pulmonary nodules (right lower lobe 8mm, left lower lobe 5mm)
• Suspicious for pulmonary metastases
• No mediastinal lymphadenopathy
• No pleural effusion

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Questions & Model Answers

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Key Teaching Points

Pattern Recognition

This pattern suggests Dedifferentiated Chondrosarcoma:

• Elderly patient with longstanding cartilage lesion
• New aggressive symptoms (night pain, rapid progression)
• Biphasic radiological appearance
• Abrupt transition between low-grade and high-grade components on imaging/histology
• Elevated ALP and LDH

Distinguish from Conventional Chondrosarcoma:

Critical Management Points

1. Recognise biphasic pattern - key to diagnosis
2. Biopsy BOTH components - sampling error can miss diagnosis
3. Stage completely - high rate of metastases at presentation
4. MDT discussion essential - complex decision-making
5. Discuss prognosis honestly - poor survival, palliative care involvement
6. Surgical resection if feasible - even in metastatic disease for palliation
7. Chemotherapy role limited - may benefit high-grade component

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Common Examiner Follow-ups

Q: "What is the difference between dedifferentiated and high-grade conventional chondrosarcoma?"

The key distinction is the abrupt transition between recognisable low-grade cartilage and high-grade non-cartilaginous sarcoma.

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Q: "Would you offer chemotherapy to this patient?"

Chemotherapy considerations:

Arguments for:

• Metastatic disease - some treatment better than none
• High-grade component may respond (osteosarcoma-like or MFH-like)
• 20-30% response rate reported

Arguments against:

• Overall survival benefit unproven
• Significant toxicity
• Limited performance status impact
• Resources for likely palliative outcome

Decision: Discuss with patient, offer if good performance status and willing. Consider doxorubicin-based regimen. Realistic expectation is disease stabilisation rather than cure.

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Q: "The patient asks about survival. How do you counsel them?"

Approach to prognostic discussion:

1. Assess patient's understanding and wishes - "What do you understand about your condition?"
2. Provide honest information - "This is a serious condition with limited treatment options"
3. Frame realistically - "Survival is typically measured in months rather than years"
4. Focus on goals - "What's most important to you right now?"
5. Emphasise quality of life - "We can control pain and maintain your independence"
6. Introduce palliative care - "Our palliative care team helps with symptom control"
7. Leave hope without false promises - "Everyone is different, but we need to plan realistically"

Key message: Honest but compassionate communication, focus on achievable goals.

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Q: "What reconstruction would you use for proximal femoral resection?"

For this patient with metastatic disease and limited prognosis: Megaprosthesis - provides rapid rehabilitation and function for remaining life.

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Related Topics

• Conventional Chondrosarcoma
• Enchondroma
• Ollier Disease and Maffucci Syndrome
• Proximal Femoral Replacement
• Bone Metastases Management
• Osteosarcoma
• Bone Sarcoma Staging