A 17-year-old boy has a distal femoral metaphyseal mass. X-ray shows a destructive lesion with a Codman's triangle and sunburst pattern. Biopsy confirms conventional osteosarcoma. According to the Enneking staging system, a high-grade intracompartmental tumor without metastasis is classified as:

• A Stage IIA ✓
• B Stage IA
• C Stage IIB
• D Stage III

Explanation

The Enneking (MSTS) surgical staging system classifies musculoskeletal sarcomas as: Stage I (low grade) — IA intracompartmental, IB extracompartmental; Stage II (high grade) — IIA intracompartmental, IIB extracompartmental; Stage III — any grade with regional or distant metastasis. Conventional osteosarcoma is high grade (Grade 2). If it is intracompartmental (confined within the bone/compartment), it is Stage IIA. Most osteosarcomas present as Stage IIB (extracompartmental) because they break through the cortex into the soft tissues. A strictly intracompartmental high-grade tumor is Stage IIA.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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