Anal cancer
Anal cancer is predominantly an HPV-driven squamous cell carcinoma of the anal canal, presenting with bleeding, a mass, pain, or pruritus (25% asymptomatic), and confirmed by anoscopy with biopsy. Definitive concurrent chemoradiation with mitomycin and a fluoropyrimidine cures most localized disease while preserving the sphincter, reserving abdominoperineal resection for persistent or recurrent tumor.
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What this article covers
- Overview
Definition: anal cancer is a malignancy of the anal canal or anal margin, predominantly squamous cell carcinoma arising from HPV-associated dysplasia, in contrast to rectal cancer, which is an…
- Epidemiology
Rare but rising: roughly 8,000 cases diagnosed yearly in the United States, with incidence increasing about 2.2% each year over the last decade.
- Risk factors
Human papillomavirus infection and anal intraepithelial neoplasia: the dominant and strongly linked risk factor.
- Pathophysiology
HPV infection of the anal transformation zone: high-risk HPV types, chiefly 16 and 18, infect the squamocolumnar junction of the anal canal, the same biology that drives cervical, vulvar, vaginal, oropharyngeal, and penile cancers.
- Clinical features
Rectal bleeding: often the earliest symptom, sometimes mistaken for hemorrhoidal bleeding.
- Differential diagnosis
Hemorrhoids: painless bright red bleeding with straining and a reducible or thrombosed perianal lump, without an indurated mass or biopsy-proven malignancy (Hemorrhoids).
- Diagnosis
Confirm the diagnosis with biopsy: there is no clinical diagnostic criteria set for anal cancer, so histology is what confirms it.
- Management
Stage first, then select curative-intent therapy: definitive concurrent chemoradiation is the first-line, organ-preserving treatment for stage I through III (localized and locally advanced) squamous…
- Complications
Permanent colostomy: required after salvage abdominoperineal resection, because curative surgery for persistent or recurrent disease must remove the anal sphincter.
- Prognosis
Localized disease is often curable: most stage I to III disease responds to combined chemoradiation with organ and sphincter preservation, avoiding surgery and colostomy.
- Prevention
HPV vaccination: the 9-valent HPV vaccine, 0.5 mL IM per dose, given routinely at age 11 to 12 years (as early as age 9); a 2-dose schedule (months 0 and 6 through 12) if started before age 15, or a…
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