A 14-year-old boy presents with progressive knee pain and a warm, tender swelling above the medial femoral condyle. X-ray shows a poorly defined lytic-sclerotic lesion in the metaphysis with periosteal reaction. Biopsy reveals malignant spindle cells in an osteoid matrix. Chest CT shows two pulmonary nodules. TNM staging (AJCC 8th edition) would classify this tumour as:
- A Stage IVA (distant metastasis to lung) ✓
- B Stage IVB (distant metastasis to non-pulmonary sites)
- C Stage III (skip metastasis in same bone)
- D Stage IIB (high-grade, extracompartmental)
Correct answer: A. Stage IVA (distant metastasis to lung)
Explanation
In the AJCC staging of bone tumours, Stage IVA refers to tumours of any grade with distant metastasis to the lung, while Stage IVB refers to metastasis to other distant sites (non-pulmonary). Pulmonary nodules indicate haematogenous spread — Stage IVA. Stage III denotes skip metastasis (discontinuous tumour in the same bone without distant spread). Stage IIB is a high-grade tumour that has broken through the cortex (extracompartmental) but has no distant metastasis.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.