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For further information, see CMDT Part 39-16: Carcinoma of the Anus
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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
Human papillomavirus (HPV) infection in > 80%
Increased risk in combined HIV and HPV infection
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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
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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
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%