Staging Systems (Enneking, AJCC)
Staging plays a crucial role in treatment planning and prognosis estimation for primary bone and soft tissue tumours. The two main systems used in orthopaedic oncology are:
Enneking Staging System (commonly used in surgical planning)
AJCC TNM Staging System (widely used in oncology)
1. Enneking Staging – Bone Sarcomas
This system includes:
Grade (G): Histological aggressiveness
T (Tumour extension): Local vs extracompartmental
M (Metastasis): Distant spread
2. Grade Classification (Enneking)
G1 (Low Grade):
Mild atypia, mitosis <1/10 HPF
Examples: ACT, parosteal osteosarcoma
G2 (High Grade):
Distinct atypia, mitosis 1–2/10 HPF
Examples: Classic osteosarcoma, Grade 2 chondrosarcoma
G3 (Anaplastic/Dedifferentiated):
Marked atypia, mitosis >2/10 HPF
Examples: Ewing sarcoma, undifferentiated chondrosarcoma
3. T & M Definitions (Enneking)
T1: Tumour within compartment
T2: Extension to soft tissue, skip metastasis, or pelvic involvement
M1: Presence of distant metastasis
4. Enneking Stage Summary Table
Stage IA
Grade 1 (low grade)
Tumour confined within the bone (T1)
No metastasis (M0)Stage IB
Grade 1
Tumour has extended beyond the compartment (T2)
No metastasis (M0)Stage IIA
Grade 2 or 3 (high grade)
Tumour confined (T1)
No metastasis (M0)Stage IIB
Grade 2 or 3
Tumour has spread beyond compartment (T2)
No metastasis (M0)Stage III
Any grade
Any tumour extent
Distant metastasis present (M1)
5. AJCC Staging – Bone Tumours (8th Edition)
More commonly used by oncologists. Uses:
T (Tumour size)
N (Lymph node involvement)
M (Metastasis site: M1a = lung, M1b = other)
Grade (G1–G4)
6. T Category Definitions (AJCC)
T1: ≤5 cm
T2: >5–10 cm
T3: >10–15 cm
T4: >15 cm
7. AJCC Bone Staging Table
StageTNMGradeIAT1N0M0G1–2IBT2–T3N0M0G1–2IIAT1N0M0G3–4IIBT2N0M0G3–4IIIT3N0M0G3–4IVAny TN1 or M1Any MAny G
8. AJCC – Soft Tissue Sarcomas (Extremity & Trunk)
Uses TNM + Grade system. Version 8 no longer considers superficial vs deep location.
Grade Definitions:
G1: Well-differentiated (e.g., liposarcoma)
G2: Moderately differentiated (e.g., leiomyosarcoma)
G3: Poorly/undifferentiated (e.g., pleomorphic or synovial sarcoma)
References
Siegel, G. W., & Biermann, J. S. OKU: Musculoskeletal Tumours 5
Choi, J. H., & Ro, J. Y. 2020 WHO Classification of Bone Tumours
Tanaka, K., & Ozaki, T. AJCC 8th Edition – Bone & Soft Tissue Tumours
