Table 1.

Multilevel subdivision of M staging.

M staging	Criteria
M1-1	1 organ, 1 metastatic lesion
M1-2	1 organ, 2 metastatic lesions
M1-3	1 organ, 3 metastatic lesions
M1-4	1 organ, 4 metastatic lesions
M1-m	1 organ, multiple metastatic lesions
M2-2	2 organs, 2 metastatic lesions
M3-3	3 organs, 3 metastatic lesions
Mm-m	> 3 organs, ≥ 5 metastatic lesions

M, metastasis; m, multiple.