Staging Anal Cancer

• TX: primary tumor cannot be assessed
• T0: no evidence of primary tumor
• Tis: carcinoma in situ (Bowen disease, high-grade squamous intraepithelial lesion [HSIL], anal intraepithelial neoplasia II-III (AIN II-III)
• T1: tumor 2 cm or less 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 (note that direct invasion of the rectal wall, perirectal skin, subcutaneous tissue, or the sphincter muscle(s) is not classified as T4)

Regional lymph nodes (N)

• Nx: regional lymph nodes cannot be assessed
• N0: no regional lymph node metastasis
• N1: metastasis in regional lymph nodes
• N1a: metastases in inguinal, mesorectal, and/or internal iliac lymph nodes
• N1b: metastases in external iliac lymph nodes
• N1c: metastases in external iliac and in inguinal, mesorectal, and/or internal iliac lymph nodes

Distant metastasis (M)

• Mx: distant metastasis cannot be assessed
• M0: no distant metastasis
• M1: distant metastasis

Involvement of para-aortic or more distant lymph nodes is considered M1

Stage 0 Tis N0 M0
Stage I T1 N0 M0
Stage II T2, T3 N0 M0
Stage IIIA T1, T2, T3 N1 M0
T4 N0 M0
Stage IIIB T4 N1 M0
Any      T N2, N3 M0
Stage IV Any T Any N M1

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