Anus & perianal area



Deputy Editor-in-Chief: Debra L. Zynger, M.D.
Raul S. Gonzalez, M.D.

Last author update: 10 December 2020
Last staff update: 6 May 2021

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PubMed Search: Anus and staging[title]

Raul S. Gonzalez, M.D.
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Cite this page: Gonzalez RS. Staging. website. Accessed June 9th, 2023.
Definition / general
  • All carcinomas of the anus, including poorly differentiated neuroendocrine carcinomas, are covered by this staging system
Essential features
  • AJCC 7th edition staging was sunset on December 31, 2017; as of January 1, 2018, use of the 8th edition is mandatory
  • Anal cancer: tumors that develop from mucosa that cannot be visualized entirely while gentle traction is placed on the buttocks
  • Perianal cancer: tumors that arise within the skin at or distal to the squamous mucocutaneous junction, can be seen entirely with gentle traction on the buttocks and are within 5 cm of the anus
  • Older terms for high grade squamous intraepithelial lesion (pTis disease) include carcinoma in situ, Bowen disease, anal intraepithelial neoplasia II-III and high grade anal intraepithelial neoplasia
ICD coding
  • ICD-10: C21.0 - Malignant neoplasm of anus, unspecified
Primary tumor (pT)
  • TX: Primary tumor not assessed
  • T0: No evidence of primary tumor
  • Tis: High grade squamous intraepithelial lesion
  • T1: Tumor ≤ 2 cm
  • T2: Tumor > 2 cm but ≤ 5 cm
  • T3: Tumor > 5 cm
  • T4: Tumor of any size invading adjacent organ(s), such as the vagina, urethra or bladder
Regional lymph nodes (pN)
  • 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 nodes
    • N1b: Metastasis in external iliac lymph nodes
    • N1c: Metastasis in external iliac with any N1a nodes
  • Notes:
    • Superior rectal (hemorrhoidal) lymph nodes are also considered regional lymph nodes, though not specifically mentioned in the pN criteria
Distant metastasis (pM)
  • M0: No distant metastasis
  • M1: Distant metastasis
  • y: preoperative radiotherapy or chemotherapy
  • r: recurrent tumor stage
Stage grouping
  • Stage 0: Tis N0 M0
  • Stage I: T1 N0 M0
  • Stage IIA: T2 N0 M0
  • Stage IIB: T3 N0 M0
  • Stage IIIA: T1 - T2 N1 M0
  • Stage IIIB: T4 N0 M0
  • Stage IIIC: T3 - T4 N1 M0
  • Stage IV: any T any N M1

Registry data collection variables
  • Tumor location
  • HIV status
  • Gender
  • Grade
  • HPV status and p16 or p18 expression
Histologic grade
  • GX: Grade cannot be assessed
  • G1: Well differentiated (low grade)
  • G2: Moderately differentiated (low grade)
  • G3: Poorly differentiated (high grade)
  • G4: Undifferentiated (high grade)
Histopathologic type
Board review style question #1
    Which of the following criteria characterizes a malignancy as an anal, rather than a perianal, tumor?

  1. Arises distal to the squamous mucocutaneous junction
  2. Cannot be entirely visualized after gentle traction on the buttocks
  3. Squamous cell or basal cell carcinoma histologically
  4. Visible only on colonoscopy
Board review style answer #1
B. Cannot be entirely visualized after gentle traction on the buttocks

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