WHO classification of anal margin tumors

The WHO classification of anal margin tumors or perianal skin tumors is:

  • intraepithelial tumors
    • Bowen disease (precursor of squamous cell carcinoma)
    • Paget disease (precursor of adenocarcinoma)
  • invasive tumors
    • squamous cell carcinoma
    • adenocarcinoma
    • basal cell carcinoma 
    • verrucous carcinoma (Buschke-Lowenstein tumor)