Table 4.

Definition of N category for American Joint Committee on Cancer (AJCC) TNM staging.

	Extent of Regional Lymph Node and/or Lymphatic Metastasis
N Category	No. of Tumor-Involved Regional Lymph Nodes	Presence of In-transit, Satellite, and/or Microsatellite Metastases
NX	Regional nodes not assessed (ie, SLNB not performed, regional nodes previously removed for another reason); Exception: pathological N category is not required for T1 melanomas, use clinical N information	No
N0	No regional metastases detected	No
N1	One tumor-involved node or any number of in-transit, satellite, and/or microsatellite metastases with no tumor-involved nodes	No
N1a	One clinically occult (ie, detected by SLNB)	No
N1b	One clinically detected	No
N1c	No regional lymph node disease	Yes
N2	Two or 3 tumor-involved nodes or any number of in-transit, satellite, and/or microsatellite metastases with one tumor-involved node
N2a	Two or 3 clinically occult (ie, detected by SLNB)	No
N2b	Two or 3, at least 1 of which was clinically detected	No
N2c	One clinically occult or clinically detected	Yes
N3	Four or more tumor-involved nodes or any number of in-transit, satellite, and/or microsatellite metastases with 2 or more tumor-involved nodes, or any number of matted nodes without or with in-transit, satellite, and/or microsatellite metastases
N3a	Four or more clinically occult (ie, detected by SLNB)	No
N3b	Four or more, at least 1 of which was clinically detected, or the presence of any number of matted nodes	No
N3c	Two or more clinically occult or clinically detected and/or presence of any number of matted nodes	Yes

Adapted from Gershenwald JE, Scolyer RA, Hess KR, et al. Melanoma of the skin. In: Amin MB, Edge SB, Greene FL, et al, eds. AJCC Cancer Staging Manual, 8^th ed., Springer International Publishing; 2017:563–585.

SLNB, sentinel lymph node biopsy.