Musculoskeletal Tumour Society Staging System


Stage 1  Benign inactive

Stage 2 Benign active

Stage 3  Benign aggressive


Stage I Low grade malignant

Stage II  High grade malignant

Stage III  Metastases to any site



- guide prognosis

- guide surgical management

- guide adjunctive therapies






A compartment is an anatomically confining space

- will resist tumour spread beyond its boundaries 


Intra-compartmental (4)

- intra-osseous

- intra fascial compartments

- superficial to deep fascia 

- par-osseous



- extension beyond above

- pelvis

- popliteal fossa

- axilla

- cubital fossa




Latent / Inactive


Non-ossifying fibroma

- benign, intracapsular, no metastatic potential

- typical clinical course is unchanging or self-limiting

- tendency to self healing





- characteristic is progressive growth

- benign, intracapsular, no metastatic

- X-ray and clinical appearance suggests active but contained growth

- without extracapsular penetration


5-10% local recurrence with curettage 

- respond well to wide excision





- locally aggressive but no metastatic potential

- benign, extracapsular but intra-compartmental

- X-ray and clinically characterised by extracapsular penetration & destructive growth


10-20% recurrence after marginal excision 

- may even recur after wide excision

- best treatment by excision with cuff of tissue




1A Low Grade Intra-compartmental

1B Low Grade Extra-compartmental


2A High Grade Intra-compartmental

2B High Grade Extra-compartmental


3 Metastasis


Low grade

- low metastatic potential

- parosteal OS


Treatment is surgery alone

- don't require systemic treatment

- tumour nodules in reactive zone but not beyond

- wide excision


High grade

- grow rapidly & metastasise early

- tumour nodules beyond reactive zone

- classis central OS


Treatment is surgery & systemic treatment