What is anal cancer screening?
Anal cancer screening looks for precancerous cell changes in higher-risk groups so they can be treated before cancer develops. It is not recommended for everyone.[1]
The idea is similar to cervical screening, because both cancers are caused by high-risk HPV types.
Why screening helps higher-risk groups
Screening the right groups can find treatable precancer, but it only helps when there is a diagnostic pathway for abnormal results.[1]
A large trial in people living with HIV found that treating high-grade precancerous lesions (HSIL) reduced progression to anal cancer, which is key evidence supporting screening in this group.[1]
How common is it?
Anal cancer is uncommon in the general population but much more frequent in some groups, especially people living with HIV and men who have sex with men who are living with HIV.[1] This difference is why screening is risk-based rather than universal.
How anal cancer develops
Most anal cancers result from persistent infection with high-risk HPV, which causes high-grade precancerous changes (HSIL) that can slowly progress to cancer over years.[1],[2]
Some people with HIV are at higher risk because their immune system clears HPV less effectively. Smoking also increases risk.
How screening is done
Symptom assessment should be distinguished from screening people without symptoms.[1],[2]
- Screening uses an anal swab for cytology (an “anal Pap”) and/or high-risk HPV testing, together with a digital anorectal examination.
- Abnormal results need high-resolution anoscopy (HRA), a magnified examination of the anal canal, with biopsy of abnormal areas.
- People with symptoms, such as bleeding or a lump, need prompt diagnostic assessment rather than screening.
Who should be screened, and what must go with it
HIV-specific guidance such as that from NYSDOH AI uses age and exposure history. For example, men who have sex with men and transgender people with HIV start at around age 35, and other people with HIV at around 45.[1] People without HIV who have other risk factors should discuss it individually.
- An anal Pap alone is not enough without access to HRA when results are abnormal.
- HPV vaccination helps prevent new infection in people within the eligible age range.
- Stopping smoking reduces risk.
How we care for you at Dr. Kris Clinic
We assess whether you are in a group that should be screened, based on age, HIV status and risk history, and explain the benefits and limits honestly. Examinations are private and judgement-free, in English or Thai.
If results are abnormal, we refer you for HRA and specialist treatment, and advise on HPV vaccination and stopping smoking. Anyone with symptoms is assessed promptly.
Frequently asked questions
Should everyone have an anal Pap?
No. Screening is recommended for higher-risk groups such as some people with HIV. Others should discuss it individually with a doctor.
Does an anal Pap hurt?
It uses a swab and takes only moments. It may feel a little uncomfortable but should not be very painful.
Does an abnormal result mean cancer?
No. Most abnormal results are cell changes. HRA and biopsy are needed to confirm what they are.
I have rectal bleeding. Should I wait for screening?
No. Symptoms need prompt diagnostic assessment at any age.
An anal Pap is not universal screening and needs a pathway for abnormal results.[1] Higher-risk groups should talk to a doctor, and anyone with symptoms should be assessed promptly.
Talk to a doctor about this
Confidential care in Surat Thani, the mainland gateway to Koh Samui, Koh Phangan and Koh Tao. Tue–Fri 17:00–20:00 · Sat–Sun 10:00–15:00 (UTC+7)
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Dr. Krida Uakridathikarn (Dr. Kris)
Board-certified family physician with certificate training in clinical sexology and sexual medicine. He works at Suratthani Hospital and provides sexual health, hormone and LGBTQ+ inclusive care at Dr. Kris Clinic. Profile and CV
References
- NYSDOH AI: Screening for Anal Dysplasia and Cancer in Adults With HIV (online guideline)
- CDC: HPV Vaccine Recommendations
- CDC STI Guidelines: Screening Recommendations
Keep reading
Main guide: HIV & STI prevention
Which STI Tests Do You Need, and When?
Syphilis: Symptoms, Testing and Stage-Based Treatment
Gonorrhoea and Chlamydia: Symptoms, Testing and Proper TreatmentThis article is general education, not personal medical advice or a promise of results. Diagnosis and treatment require assessment by a doctor. Content reflects the cited sources as of the update date.