Table 1. Current N staging system and several proposed N categories.

Stage	Definition
7th TNM[39]
N0	No regional lymph node metastasis
N1	Metastasis in a single inguinal lymph node
N2	Metastasis in multiple or bilateral inguinal lymph nodes
N3	Extranodal extension of LNM or pelvic lymph node(s) unilateral or bilateral
Lont, et al.[18]
N0	No evidence of lymph node metastasis
N1	Metastasis in 1 or 2 inguinal lymph nodes without extracapsular growth
N2	Metastasis in more than 2 lymph nodes metastasis with extracapsular growth
N3	Evidence of involvement of pelvic lymph nodes or bilateral nodes with extgracapsular growth
Leijte, et al.[20]
N0	No regional lymph node metastasis
N1	Unilateral inguinal metastasis, mobile
N2	Bilateral inguinal metastasis, mobile
N3	Fixed inguinal metastasis or metastasis in pelvic lymph nodes(s)
Zhu and Ye
N0	No regional lymph node metastasis
N1a	Metastasis in a single inguinal lymph node less than 5 mm
N1b	Metastasis in a single inguinal lymph node 5 mm or greater
N2a	Metastasis in 2 or 3 unilateral inguinal lymph nodes
N2b	Metastasis in more than 4 unilateral or bilateral inguinal lymph nodes
N3	Extranodal extension of LNM or pelvic lymph node(s) unilateral or bilateral