Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 39-16: Carcinoma of the Anus + Key Features Download Section PDF Listen +++ ++ 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 Download Section PDF Listen +++ ++ Anal bleeding Pain Local tumor 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 + Diagnosis Download Section PDF Listen +++ ++ 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 + Treatment Download Section PDF Listen +++ ++ 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 either carboplatin and paclitaxel or 5-fluorouracil in combination with cisplatin 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 Should be strongly considered in the second-line setting in patients with good performance status 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%