A 16-year-old boy has a distal femoral osteosarcoma confirmed on biopsy. Pre-operative chemotherapy (neoadjuvant) is given for 10 weeks. The resected specimen shows 95% tumour necrosis. According to the Huvos grading system, this response is classified as:

• A Grade III — good response (>90% but <100% necrosis) ✓
• B Grade I — poor response (<50% necrosis)
• C Grade II — partial response (50–90% necrosis)
• D Grade IV — complete response (100% necrosis)

Explanation

The Huvos grading system assesses histological response of osteosarcoma to neoadjuvant chemotherapy: Grade I <50% necrosis (poor), Grade II 50–90% (partial), Grade III >90% but <100% (good), Grade IV 100% necrosis (complete). Grades III and IV are considered good responders and correlate with improved 5-year survival (~70–80%). Poor responders (Grade I–II) have worse prognosis and may benefit from adjuvant chemotherapy regimen change.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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