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For further information, see CMDT Part 39-16: Carcinoma of the Anus

Key Features

  • Carcinoma of the anus is relatively rare: only 1–2% of all cancers of the large intestine and anus

  • Squamous cancers (keratinizing, transitional cell, and cloacogenic), 80%; adenocarcinomas, 20%

  • Increased incidence among

    • People practicing receptive anal intercourse

    • Those with a history of anorectal warts

    • Those with HIV infection

  • Human papillomavirus (HPV) infection in > 80%

  • Increased risk in combined HIV and HPV infection

Clinical Findings

  • Anal bleeding

  • Pain

  • Local mass

  • The lesion is often confused with hemorrhoids or other common anal disorders

  • Tumors tend to become annular, invade the sphincter, and spread upward via the lymphatics into the perirectal mesenteric lymphatic nodes


  • CT or MRI scans of the abdomen and pelvis are required to identify regional lymphadenopathy or metastatic disease at diagnosis

  • PET imaging may be used in conjunction


  • Wide local excision for small (< 3 cm) superficial lesions of the perianal skin

  • Combined-modality therapy for tumors invading the sphincter or rectum: external radiation with simultaneous chemotherapy (fluorouracil plus mitomycin)

  • Local control achieved in approximately 80% of patients

  • Radical surgery (abdominoperineal resection) for patients in whom chemotherapy and radiation therapy fail

  • Metastatic disease is generally treated with carboplatin and paclitaxel

  • Checkpoint inhibitor therapy with either nivolumab or pembrolizumab has been shown in small studies to result in disease control in up to 46% of patients with chemotherapy-refractory, metastatic or unresectable disease

  • 5-year survival rate

    • 81% for localized (stages I–III) disease

    • ~30% for metastatic (stage IV) disease

  • In a large controlled trial, HPV vaccination of healthy men (16–26 years old) who have sex with men decreased the incidence of anal intraepithelial neoplasia by 50%

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