Histological assessment of an osteosarcoma resection specimen after neoadjuvant chemotherapy shows 95% tumor necrosis. This Huvos grade response is classified as:

• A Grade III — good response (90–99% necrosis) ✓
• B Grade I — poor response (>50% viable tumor)
• C Grade II — partial response (50–89% necrosis)
• D Grade IV — complete response (100% necrosis)

Explanation

The Huvos grading system assesses the histological response of osteosarcoma to neoadjuvant chemotherapy: Grade I = <50% necrosis (poor); Grade II = 50–89% necrosis (partial); Grade III = 90–99% necrosis (good response — viable foci may remain); Grade IV = 100% necrosis (complete pathological response). Grade III or IV response (≥90% necrosis) is considered a favorable response, predicts better event-free survival, and supports continuation of the same chemotherapy regimen. Patients with Grade I/II response may benefit from regimen modification.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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