Anal carcinoma - exploring the epidemiology, risk factors, pathophysiology, diagnosis, and treatment

Table 3 Tumor, node, and metastasis classification system for anal cancer

Primary tumor	Characteristics
TX	Primary tumor cannot be assessed
T0	No evidence of primary tumor
Tis	HSIL (previously termed carcinoma in situ, Bowden disease, anal intraepithelial neoplasia II-III, high-grade anal intraepithelial neoplasia)
T1	Tumor ≤ 2 cm in greatest dimension
T2	Tumor > 2 cm but ≤ 5 cm in greatest dimension
T3	Tumor > 5 cm in greatest dimension
T4	Tumor of any size invades adjacent organ(s) (e.g., vagina, urethra, bladder)
Lymph nodes
NX	Regional lymph nodes cannot be assessed
N0	No regional lymph node metastasis
N1	Metastasis in inguinal, mesorectal, internal iliac, or external iliac nodes
	N1a: Metastasis in inguinal, mesorectal, or internal iliac lymph nodes
	N1b: Metastasis in external iliac lymph nodes
	N1c: Metastasis in external iliac with any N1a nodes
Metastasis
M0	No distant metastasis
M1	Distant metastasis

HSIL: High-grade squamous intraepithelial lesion.