Updated: 6/18/2021

Bone Tumor Staging Systems

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  • Introduction
    • Prognosis of bone cancer depends on the following variables
      1. overall stage of disease (incorporates all of the below)
      2. presence of metastasis
      3. skip (discontinous) lesions within the same bone
      4. histologic grade
      5. tumor size
    • The are two staging systems that are commonly used:
      • MSTS or Enneking System
      • AJCC Staging System
  • MSTS (Enneking) Staging System
    • Introduction
      • most popular and useful for orthopaedic surgeons
      • two systems - one for malignant lesions and one for benign lesions
        • malignant lesions are defined using Roman numerals (e.g. I, II, III)
          • see table below
          • e.g. osteosarcoma most commonly presents as stage IIB
        • benign lesions are defined using Arabic numbers (1,2,3)
          • 1 = latent lesion
            • e.g. non-ossifying fibroma
            • enchondroma
          • 2 = active lesion
            • e.g. ABC, UBC
            • chondromyxoid fibroma
            • chondroblastoma
          • 3 = aggressive lesion
            • e.g. giant cell tumor of bone
      • MSTS Staging for Malignant tumors
        Stage
        Grade
        Site
        Metastasis
        IA
        Low Grade
        T1 - intracompartmental
        M0 (none)
        IB
        Low Grade
        T2 - extracompartmental
        M0 (none)
        IIA
        High Grade
        T1 - intracompartmenta
        M0 (none)
        IIB
        High Grade
        T2 - extracompartmental
        M0 (none)
        III
        Metastatic
        T1 or T2 - intra or extra-compartmental
        M1 (regional or distant)
    • Tumor Compartments
      • intracompartmental
        • bone tumors are confined within the cortex of the bone
      • extracompartmental
        • bone tumors extend beyond the bone cortex
    • Tumor Grade
      • histologically, tumors are graded based on the percentage of cellular atypia
        • low grade tumors
          • low metastatic potential
          • e.g. parosteal osteosarcoma
        • high grade tumors
          • greater metastastatic potential
          • e.g. intramedullary osteosarcoma, Ewing's sarcoma, dedifferentiated chondrosarcoma
  • AJCC Staging System
    • AJCC Staging System
      Stage
      Grade
      Size
      Depth
      Node
      Metastasis
      5 yr. survival
      IA
      Low Grade
      < 8cm
      Any
      None
      None
      98%
      IB
      Low Grade
      > 8cm
      Any
      None
      None
      IIA
      High Grade
      < 8cm
      Any
      None
      None
      82%
      IIB
      High Grade
      > 8cm
      Superficial
      None
      None
      82%
      III
      Any
      Discontinuous (skip) lesion
      Deep
      None
      None
      52%
      IVA
      Any 
      Any
      Any
      None
      Lung
      IVB
      Any
      Any
      Any
      Present
      Other than lung
      30%
    • Prognosis for soft tissue tumors depends on
      • grade
        • low grade: G1 and G2
        • high grade: G3 and G4
      • size
        • T1: < 8 cm
        • T2 > 8 cm
      • nodes
        • N0: no regional nodes
        • N1: regional nodes
      • metastasis
        • presence of distant metastasis automatically elevates patient to stage IV disease

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(OBQ05.7) A 13-year-old girl presents with an isolated distal femur osteosarcoma that extends into the soft tissue. Work-up is negative for metastasis, but biopsy reveals a high grade lesion. What is the stage of this tumor by the Musculoskeletal Tumor Society system?

QID: 44
1

I A

0%

(1/1925)

2

II A

7%

(136/1925)

3

I B

3%

(54/1925)

4

II B

85%

(1629/1925)

5

III

5%

(95/1925)

L 1 D

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