This case-sensitive code system http://fhir.ch/ig/ch-crl/CodeSystem/nkrs-torontotierIImanualstaging defines the following codes:

Code	Definition
M0	No visible disease on imaging (MRI brain and spine) beyond primary site of disease and no tumour cells in the cerebrospinal fluid (CSF)
M1	Tumour cells in the CSF
M2	Visible metastasis in brain
M3	Visible metastasis in spine or visible metastasis in cervicomedullary (junction)
M4	Metastasis outside of the central nervous system
Localised	Used for Ewing’s sarcoma or osteosarcoma : tumour confined to the area of origin including regional lymph nodes Although more detailed staging systems exist their clinical and prognostic value is limited, multi-tiered staging systems were not deemed appropriate
Metastatic	Used for Ewing’s sarcoma or osteosarcoma with distant metastases present at diagnosis. Although more detailed staging systems exist their clinical and prognostic value is limited, multi-tiered staging systems were not deemed appropriate