Updated: 6/29/2016

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
Stage
Grade
Site (1)
Metastasis
IA Low Grade T1 - intracompartmental M0 (none)
IB Low Grade T2 - extracompartmental M0 (none)
IIA High Grade T1 - intracompartmental M0 (none)
IIB  High Grade T2 - extracompartmental M0 (none)
III Metastatic T1 - intracompartmental M1 (regional or distant)
III Metastatic T2 - extracompartmental 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

Stage
Grade
Size
Depth
Node
Metastasis
5 yr. survival
IA
Low Grade
< 8cm
any
none
none
98%
IB
Low Grade
> 8cm
   
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
 
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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Questions (4)
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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? Review Topic

QID: 44
1

I A

0%

(1/1527)

2

II A

6%

(92/1527)

3

I B

2%

(37/1527)

4

II B

87%

(1322/1527)

5

III

5%

(70/1527)

ML 1

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