A 16-year-old boy with osteosarcoma of the distal femur undergoes staging with MRI, chest CT, and bone scan. MRI shows tumor confined to bone with a reactive zone but no skip lesions; chest CT is clear; bone scan shows no distant foci. According to the Enneking/MSTS surgical staging system, this is best staged as:

• A Stage IA — low-grade, intracompartmental
• B Stage IIB — high-grade, extracompartmental
• C Stage III — any grade with regional or distant metastasis
• D Stage IIA — high-grade, intracompartmental ✓

Explanation

The Enneking/MSTS system stages bone tumors by grade (I = low, II = high), compartment (A = intracompartmental, B = extracompartmental), and metastasis (III). Osteosarcoma is histologically high-grade (grade II) by definition. Here the tumor is confined to bone (intracompartmental) without skip lesions or distant spread, making it Stage IIA. Stage IIB would require extracompartmental extension (through cortex into soft tissue). Stage III denotes regional nodal or distant metastasis. Stage IA denotes low-grade intracompartmental — not applicable to osteosarcoma.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.