A 16-year-old male presents with a destructive lesion of the distal femur with Codman's triangle and a sunburst pattern on X-ray. MRI shows the tumor confined to bone without skip metastases. According to Enneking's staging system, this tumor is best classified as:
- A Stage IIA (high-grade, intracompartmental) ✓
- B Stage IA (low-grade, intracompartmental)
- C Stage IIB (high-grade, extracompartmental)
- D Stage IIIB (any grade, with metastases, extracompartmental)
Correct answer: A. Stage IIA (high-grade, intracompartmental)
Explanation
Enneking staging for bone tumors: Grade (G1 = low, G2 = high), Site (T1 = intracompartmental, T2 = extracompartmental), Metastases (M0/M1). Osteosarcoma is always Grade 2 (high-grade). If MRI shows the lesion confined within the bone/compartment without extraosseous extension, it is T1, giving Stage IIA. If it has broken through the cortex or periosteum into adjacent soft tissue it becomes IIB. Stage IIIB requires distant metastases. The classic X-ray features (Codman's triangle, sunburst) confirm osteosarcoma, which is by definition high-grade.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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