Table 1.

American Joint Committee on Cancer (AJCC) classification (8th ed): tumor–node–metastasis (TNM) classification9

T	X	0	Is	1	2	3	4
	Not assessable	Not present	In situ	≤2 cm	>2 and ≤5 cm	>5 cm	Invasion of bone, muscle, fascia, or cartilage

cN	X	0	1	2	3
	Not assessable (e.g., the regional lymph nodes were already removed earlier)	No clinically or radiologically detected metastasis to regional lymph nodes	Clinically detected metastasis to one or more locoregional lymph nodes	In-transit metastasis without nodal metastasis	In-transit metastasis with nodal metastasis

pN	X	0	1a(sn)	1a	1b	2	3
	Not assessable (e.g., the regional lymph nodes were already excised earlier or were not excised during treatment)	Not present	Clinically occult micrometastasis now detected by SLNB	Clinically occult metastasis to one or more locoregional lymph nodes	Clinically detected metastasis to one or more locoregional lymph nodes	In-transit metastasis without nodal metastasis	In-transit metastasis with nodal metastasis

M	0	1	1a	1b	1c
	Not present	Metastasis beyond the locoregional lymph drainage region	Metastasis to not adjacent skin, subcutaneous tissue, or distant lymph nodes	Metastasis to the lungs	Metastasis to other regions

SLNB sentinel lymph node biopsy