Table 2 Main differences in staging and treatment stratification between anal and rectal cancer

Typical histology

Squamous cell carcinoma

Adenocarcinoma

Treatment

– Low risk (T1-stage): local excision or local radiotherapy

– Low risk: surgery only (total mesorectal excision)

– High risk (≥ T2-stage): definitive chemoradiotherapy

– Intermediate and high-risk: neoadjuvant (chemo)radiotherapy

T-stage definitions^a

Primarily based on size (largest dimension):

Primarily based on depth of invasion:

T1—tumour ≤ 2 cm

T1—tumour invades submucosa

T2—tumour > 2 cm but ≤ 5 cm

T2—tumour invades muscularis propria

T3—tumour > 5 cm

T3—tumour invades perirectal fat

T4—tumour of any size that invades adjacent organs

T4—tumour invades peritoneum (T4a) or adjacent organs/structures (T4b)

N-stage definitions^a

Primarily based on location of regional N+ nodes:

Primarily based on number of regional N + nodes:

N0 – no N+ nodes

N0 – no N+ nodes

N1a – N+ nodes in inguinal, mesorectal and/or internal iliac (including obturator) regions

N1 – 1–3 N+ nodes

N1b – N+ nodes in external iliac region

N2 – ≥ 4 N+ nodes

N1c – N+ nodes in N1a and N1b regions