Part of Cancer staging guidance sheets
Anal and perianal skin (ICD10 C21)
Introduction
This is the data sheet for TNM 9th edition staging of anal canal and perianal skin data (ICD10 C21)
For more detailed information regarding TNM staging, please see pages 79-81 of the UICC TNM 9 book.
Stage groupings
|
Stage Group |
T stage |
N stage |
M stage |
|---|---|---|---|
|
Stage 0 |
Tis |
N0 |
M0 |
|
Stage I |
T1 |
N0 |
M0 |
|
Stage IIA |
T2 |
N0 |
M0 |
|
Stage IIB |
T1, T2 |
N0 |
M0 |
|
Stage IIIA |
T3 |
N0, N1 |
M0 |
|
Stage IIIB |
T4 |
N0 |
M0 |
|
Stage IIIC |
T4 |
N1 |
M0 |
|
Stage IV |
Any T |
Any N |
M1 |
TNM clinical classification
T - primary tumour
|
T value |
Description |
|---|---|
|
cTX |
Primary tumour cannot be assessed |
|
cT0 |
No evidence of primary tumour |
|
cTis |
Carcinoma in situ, high‐grade squamous intraepithelial lesion (HSIL), anal intraepithelial neoplasia II–III (AIN II–III) anal squamous intraepithelial neoplasia H (ASIN-H)1 |
|
cT1 |
Tumour 2 cm or less in greatest dimension |
|
cT2 |
Tumour more than 2 cm but not more than 5 cm in greatest dimension |
|
cT3 |
Tumour more than 5 cm in greatest dimension |
|
cT4 |
Tumour of any size invades adjacent organ(s), e.g., vagina, urethra, bladder2 |
Note:
1AJCC does not include Tis
2Direct invasion of the rectal wall, perianal skin, subcutaneous tissue, or the sphincter muscle(s) alone is not classified as T4
N - regional lymph nodes
|
N value |
Description |
|---|---|
|
cNX |
Regional lymph nodes cannot be assessed |
|
cN0 |
No regional lymph node metastasis |
|
cN1 |
Metastasis in regional lymph node(s) cN1a - Metastases in inguinal, mesorectal, and/or internal iliac nodes cN1b - Metastases in external iliac nodes cN1c - Metastases in external iliac and in inguinal, mesorectal and/or internal iliac nodes |
M - distant metastasis
|
M value |
Description |
|---|---|
|
M0 |
No distant metastasis |
|
M1 |
Distant Metastasis |
TNM pathological classification
pT - primary tumour
The pT & pN categories correspond to the cT and cN categories as per above.
pN - regional lymph nodes
| pN value | Description |
|---|---|
|
pN0 |
Histological examination of a regional perirectal/pelvic lymphadenectomy specimen will ordinarily include 12 or more lymph nodes; histological examination of an inguinal lymphadenectomy specimen will ordinarily include 6 or more lymph nodes. If the lymph nodes are negative, but the number ordinarily examined is not met, classify as pN0. |
Last edited: 16 January 2026 3:57 pm
