Anal precancers (also known as Anal Intraepithelial Neoplasia or AIN) are growths and/or changes in the skin cells in the anal region. The existence of a 'precancerous' condition is not a cancer diagnosis, which is very important to remember. These conditions are very important precursors to cancer, however, and must be monitored, and treated if appropriate, to reduce the risk of them developing into cancer.
Regular screening, monitoring and rapid treatment are the best ways to protect yourself if you think you may be at risk. We hope the information you find here will help you identify and manage any potentially precancerous conditions.
What is Anal Intraepithelial Neoplasia (AIN)?
There are many types of growths that can develop in the anus, but not all of them are cancerous. Some start off as non-cancerous (or 'benign') but can later develop into cancer. It is these growths, the ones with the potential to become cancerous that are specifically referred to as 'precancerous'. Understanding the difference is important: a precancer diagnosis is not a cancer diagnosis, but it does require monitoring and, in some cases, treatment.
All growths and abnormal changes in the epithelial (skin) cells in and around the anal area are known as AIN (anal intraepithelial neoplasia). These changes are associated with infection with HPV (the human papillomavirus), which is a risk factor for anal cancer.
You may be familiar with these kinds of changes due to knowledge of, or experience with, cervical precancer. Cervical precancer is also caused by HPV and causes similar lesions on the cells of the cervix and anus. Unlike cervical precancer, both men and women are at risk of anal precancer because both men and women have anuses.
Changes and growths can develop on the outside of the anus as well as on the inside – and sometimes in both places at once. Symptoms include bleeding and itching in this area, although sometimes there are no symptoms at all. In the majority of cases, AIN will disappear by itself and will not develop any further.
AIN is histologically classified based on the proportion of the anal epithelium occupied by dysplastic (abnormal) cells. The condition exists on a spectrum from low-grade to high-grade disease, and the grading system is used to guide treatment decisions and monitoring frequency.
Please remember: If you have unusual itching or bleeding in this region, please go to your medical provider to discuss your symptoms as soon as possible. Even with treatment and monitoring it is possible for precancerous AIN to develop into anal cancer.
There are three different levels of AIN: AIN 1, AIN 2, and AIN 3, described below.
AIN 1
AIN 1 is not considered precancerous. AIN 1 is also known as 'mild dysplasia', or LSIL, which means 'low-grade squamous intraepithelial lesion'. Dysplasia is the general term for all abnormal changes in cells. The dysplasia is classified by the severity of the changes, i.e. mild, moderate or severe. These cells often look very similar to normal, healthy cells.
Anal warts, also called condyloma, are a type of AIN 1. As they are easily identifiable, warts are usually how people find out about their anal HPV infection. Warts are usually caused by HPV types 6 and 11.
In AIN 1, dysplastic cells are limited to the lower third of the epithelial layer. The immune system often clears these low-grade lesions spontaneously, and regression rates are high, particularly in immunocompetent individuals.
AIN 2
AIN 2 is classified as moderate dysplasia, or HSIL (high-grade squamous intraepithelial lesion), and represents an intermediate stage in which dysplastic cells extend into the middle third of the epithelial layer. AIN 2 is considered precancerous. Like AIN 3, it is most commonly associated with high-risk HPV types, particularly HPV 16 and 18.
AIN 2 lesions may regress spontaneously, remain stable, or progress to AIN 3 or invasive cancer, making monitoring essential. Given the difficulty of distinguishing AIN 2 from AIN 3 on biopsy, many clinicians manage AIN 2 similarly to AIN 3 in high-risk populations.
AIN 3
AIN 3 represents severe dysplasia, also known as HSIL, where abnormal cells occupy the full thickness of the epithelial layer. AIN 2 and AIN 3 are also known as 'moderate to severe dysplasia'. Most cases of AIN 2 and AIN 3 stay the way they are (sometimes for decades) or go away on their own. However, if an individual does not regularly visit a doctor regarding their AIN to be monitored and/or treated, there is the risk that they might develop into cancer.
There is no completely accurate way of determining whether someone's AIN 2 or AIN 3 will turn into cancer, or how long this will take. Careful and frequent screening and monitoring is therefore recommended. AIN 2 and AIN 3 are most commonly caused by HPV types 16 and 18. AIN 2 and AIN 3 tend to be more common in HIV-positive individuals, although HIV-negative individuals develop them as well.
AIN 3 is considered the direct precursor to invasive squamous cell carcinoma of the anus. Studies estimate that the rate of progression from untreated AIN 3 to invasive cancer ranges from approximately 1–13% over several years, with higher rates in immunocompromised individuals. This underscores the importance of early detection and treatment.
Diagnosis
Diagnosis of AIN typically involves a combination of clinical examination and tissue biopsy. A biopsy, obtained during high-resolution anoscopy (HRA), is the definitive method for confirming a diagnosis and grading the lesion. HRA allows the clinician to apply acetic acid (vinegar) to the anal canal, which causes dysplastic tissue to turn white (acetowhitening), making abnormal areas visible under magnification before biopsy is taken. Pathological examination of the biopsy sample determines the AIN grade.
Symptoms, when present, may include anal itching, bleeding, or discomfort, though many people with AIN are entirely asymptomatic. Because AIN is frequently found incidentally during screening or evaluation of other conditions, proactive screening in at-risk populations is critical to diagnosis.
Screening
If you think you may have AIN or are at risk, it is suggested that you have a clinician screen you. Screening involves visual inspection. However, appropriate and accurate screening should also include additional methods, as a visual check alone can fail to diagnose AIN that is inside the anal canal and any subtle changes. Additional screening options include:
- Digital ano-rectal exam (DARE): a doctor places his or her fingers inside the anal canal to feel for abnormalities. The purpose of this test is to look for abnormal masses or growths, so if you think you may have precancer, request this additional testing.
- Anal Pap test: similar to a routine cervical pap test and involves sampling cells inside the anus to detect changes and abnormalities.
- Anoscopy: a tube called an anoscope is placed inside the anus and a strong light illuminates the tissue.
- High-resolution anoscopy (HRA): a more advanced anoscope with a high-resolution magnifying glass is used to examine and evaluate the tissue in the anus. This is the most precise examination for anal cancer and precancer. Learn more about HRA.
Screening Guidelines
Routine screening guidelines for anal cancer or precancer have not yet been universally adopted because there have not yet been enough studies for the government and medical communities to recommend routine screening. The predominant guidelines tend to focus on HIV-positive individuals. New York State, for example, recommends annual anal pap smears for HIV-positive men and women.
There is increasing evidence to support screening for precancers. The NIH has funded the ANCHOR study, the first randomised controlled trial for anal precancer screening efficacy and treatment.
The ANCHOR study (Anal Cancer HSIL Outcomes Research), published in the New England Journal of Medicine in 2022, found that treating HSIL (AIN 2/3) in HIV-positive individuals reduced the risk of progression to invasive anal cancer by 57% compared to active monitoring alone. This landmark finding has strengthened calls for broader, risk-stratified screening guidelines.
The International Anal Neoplasia Society (IANS) and several major HIV medicine organisations recommend anal cancer screening for high-risk groups, including HIV-positive men who have sex with men (MSM), HIV-positive women, and immunocompromised individuals such as solid organ transplant recipients. Screening intervals and modalities vary by guideline and risk group.
It is hoped that universal standards of care will be developed from ongoing research and embraced by the government and medical community.
Where Can I Get Screened?
Please see our Medical Resources page to find a clinician providing screening services in your area.
Treatment for AIN
Precancerous conditions can disappear on their own, without needing treatment. However, it is important to be frequently monitored if you are presenting with dysplasia. Even with care and treatment, recurrence is still possible, especially for individuals considered high risk, such as people living with HIV.
AIN 1 and 2
AIN 1 is generally managed conservatively with active surveillance rather than immediate intervention, given its high rate of spontaneous regression. For AIN 2, management decisions are individualised and take into account the patient's immune status, the extent of disease, and patient preference. In immunocompetent patients with AIN 2, watchful waiting with close follow-up (typically every 6–12 months) may be appropriate. In immunocompromised patients, treatment is more often recommended. Topical therapies such as imiquimod or 5-fluorouracil (5-FU) cream may be used for both AIN 1 and AIN 2, particularly for external lesions.
AIN 3
Given its status as a direct precursor to invasive cancer, AIN 3 generally warrants active treatment rather than surveillance alone. Treatment choice depends on the size, location, and extent of disease, as well as the patient's overall health. Options include topical therapies for small, superficial lesions, or procedural interventions such as fulguration, laser therapy, or surgical excision for more extensive disease. Regular follow-up after treatment is essential, as recurrence rates are significant, particularly in HIV-positive individuals.
Excision
Surgical excision involves the physical removal of dysplastic tissue, typically under local or general anaesthesia. It is particularly useful for well-defined, accessible lesions and allows for histological examination of the excised tissue to confirm the diagnosis and ensure clear margins. Excision may be performed as an office-based procedure for small external lesions or in a surgical setting for larger or internal lesions. There is a risk of scarring, stricture, or incontinence with more extensive excisions.
Fulguration
Fulguration (also called electrocautery or hyfrecation) uses an electrical current to destroy dysplastic tissue. It is a commonly used office-based procedure for both internal and external AIN lesions. The technique is relatively quick and well-tolerated, though it may require multiple treatment sessions for larger lesions. Post-procedure discomfort and wound healing are typical considerations.
Laser Therapy
Infrared coagulation (IRC) and CO₂ laser ablation are minimally invasive techniques used to destroy AIN lesions. IRC uses infrared light to cauterise abnormal tissue and is particularly well-suited for treating internal lesions within the anal canal. CO₂ laser offers precise tissue destruction with a controlled depth of penetration and is commonly used for both internal and external disease. Both approaches generally require local anaesthesia and may need to be repeated.
Surgery
More extensive surgical resection may be indicated in cases of widespread or recurrent high-grade AIN, or when there is concern for occult invasive cancer. Wide local excision allows for pathological assessment of the resected specimen. However, given the risk of functional complications, including anal stenosis and impaired continence, extensive surgery is typically reserved for cases where less invasive treatments have failed or where invasion cannot be excluded.
Risk Factors
Other risk factors that may increase your chances of getting anal precancer include smoking, being a transplant recipient, and being an older individual (50–80 years old). The types of changes that lead to anal precancer are also found in the cervix, vagina, vulva, and penis.
HPV
These changes are associated with infection with HPV (the human papillomavirus). AIN 1 is most commonly associated with low-risk HPV types 6 and 11, while AIN 2 and AIN 3 are most commonly caused by HPV types 16 and 18.
HPV is the most important risk factor for the development of anal dysplasia and anal cancer. HPV 16 is responsible for the majority of HPV-attributable anal cancers worldwide. Persistent infection with high-risk HPV strains — rather than transient infection — is what drives the development of high-grade precancerous lesions. HPV is transmitted through skin-to-skin contact, including sexual contact. Receptive anal intercourse is an independent risk factor for anal HPV acquisition, though HPV-related anal disease can occur in individuals with no history of anal intercourse.
HIV
AIN 2 and AIN 3 tend to be more common in HIV-positive individuals, although HIV-negative individuals develop them as well.
HIV infection significantly increases the risk of developing anal precancer and cancer. HIV impairs the immune system's ability to clear HPV infection, leading to higher rates of HPV persistence, co-infection with multiple HPV types, and more rapid progression from low-grade to high-grade lesions. Men who have sex with men (MSM) living with HIV have among the highest rates of anal HSIL and anal cancer of any population. Even with effective antiretroviral therapy (ART), HIV-positive individuals remain at elevated risk compared to the general population, underscoring the need for regular anal cancer screening in this group.
Crohn's Disease
Crohn's disease, a chronic inflammatory bowel condition, is associated with an increased risk of anal and colorectal dysplasia and cancer. Perianal Crohn's disease which causes chronic inflammation, fistulae, and scarring in the anal region creates a local environment that may promote dysplastic change. Studies have shown that individuals with longstanding perianal Crohn's disease have a higher incidence of anal squamous cell carcinoma compared to the general population. Immunosuppressive therapies used to manage Crohn's disease may further compound this risk. As a result, clinicians are increasingly advocating for anal cancer screening in patients with perianal Crohn's disease.
HPV Vaccination
HPV vaccination is a key primary prevention strategy against anal precancer and cancer. The nonavalent HPV vaccine (Gardasil 9) protects against nine HPV types, including the high-risk types 16 and 18 (responsible for the majority of anal cancers) and the low-risk types 6 and 11 (which cause anal warts/AIN 1). The vaccine is most effective when administered prior to HPV exposure, ideally before sexual debut.
In the United States, the Advisory Committee on Immunization Practices (ACIP) recommends routine HPV vaccination for all individuals up to age 26, with shared clinical decision-making for those aged 27–45. Studies have demonstrated that HPV vaccination significantly reduces the incidence of anal HSIL in vaccinated populations. For individuals already diagnosed with AIN, vaccination may still be beneficial as it can provide protection against HPV types not yet acquired.
Regular screening, monitoring and rapid treatment remain the best ways to protect yourself if you think you may be at risk, alongside HPV vaccination as a preventive measure.
More Information
Learn more about anal cancer detection and prevention in this webinar from our Expert Hour series: Anal Cancer Detection and Prevention. Dr. Jessica D. Korman, a gastroenterologist at Capital Digestive Care in Washington, DC, discusses anal cancer signs and symptoms, the importance of a digital anorectal exam and high-resolution anoscopy, when a hemorrhoid is not a hemorrhoid, emerging research on anal precancer, and the HPV vaccine and its role in preventing cancer.
Peer-to-Peer Support Program
Looking for someone to talk to about your anal cancer diagnosis? We are here to help.
Anal precancers (also known as Anal Intraepithelial Neoplasia or AIN) are growths and/or changes in the skin cells in the anal region. The existence of a ‘precancerous’ condition is not a cancer diagnosis, which is very important to remember. These conditions are very important precursors to cancer, however, and must be monitored, and treated if appropriate, to reduce the risk of them developing into cancer.
Regular screening, monitoring and rapid treatment are the best ways to protect yourself if you think you may be at risk. We hope the information you find here will help you identify and manage any potentially precancerous conditions.
What is Anal Intraepithelial Neoplasia (AIN)?
There are many types of growths that can develop in the anus, but not all of them are cancerous. Some start off as non-cancerous (or ‘benign’) but can later develop into cancer. It is these growths, the ones with the potential to become cancerous that are specifically referred to as ‘precancerous’. Understanding the difference is important: a precancer diagnosis is not a cancer diagnosis, but it does require monitoring and, in some cases, treatment.
All growths and abnormal changes in the epithelial (skin) cells in and around the anal area are known as AIN (anal intraepithelial neoplasia). These changes are associated with infection with HPV (the human papillomavirus), which is a risk factor for anal cancer.
You may be familiar with these kinds of changes due to knowledge of, or experience with, cervical precancer. Cervical precancer is also caused by HPV and causes similar lesions on the cells of the cervix and anus. Unlike cervical precancer, both men and women are at risk of anal precancer because both men and women have anuses.
Changes and growths can develop on the outside of the anus as well as on the inside – and sometimes in both places at once. Symptoms include bleeding and itching in this area, although sometimes there are no symptoms at all. In the majority of cases, AIN will disappear by itself and will not develop any further.
AIN is histologically classified based on the proportion of the anal epithelium occupied by dysplastic (abnormal) cells. The condition exists on a spectrum from low-grade to high-grade disease, and the grading system is used to guide treatment decisions and monitoring frequency.
Please remember: If you have unusual itching or bleeding in this region, please go to your medical provider to discuss your symptoms as soon as possible. Even with treatment and monitoring it is possible for precancerous AIN to develop into anal cancer.
There are three different levels of AIN: AIN 1, AIN 2, and AIN 3, described below.
AIN 1
AIN 1 is not considered precancerous. AIN 1 is also known as ‘mild dysplasia’, or LSIL, which means ‘low-grade squamous intraepithelial lesion’. Dysplasia is the general term for all abnormal changes in cells. The dysplasia is classified by the severity of the changes, i.e. mild, moderate or severe. These cells often look very similar to normal, healthy cells.
Anal warts, also called condyloma, are a type of AIN 1. As they are easily identifiable, warts are usually how people find out about their anal HPV infection. Warts are usually caused by HPV types 6 and 11.
In AIN 1, dysplastic cells are limited to the lower third of the epithelial layer. The immune system often clears these low-grade lesions spontaneously, and regression rates are high, particularly in immunocompetent individuals.
AIN 2
AIN 2 is classified as moderate dysplasia, or HSIL (high-grade squamous intraepithelial lesion), and represents an intermediate stage in which dysplastic cells extend into the middle third of the epithelial layer. AIN 2 is considered precancerous. Like AIN 3, it is most commonly associated with high-risk HPV types, particularly HPV 16 and 18.
AIN 2 lesions may regress spontaneously, remain stable, or progress to AIN 3 or invasive cancer, making monitoring essential. Given the difficulty of distinguishing AIN 2 from AIN 3 on biopsy, many clinicians manage AIN 2 similarly to AIN 3 in high-risk populations.
AIN 3
AIN 3 represents severe dysplasia, also known as HSIL, where abnormal cells occupy the full thickness of the epithelial layer. AIN 2 and AIN 3 are also known as ‘moderate to severe dysplasia’. Most cases of AIN 2 and AIN 3 stay the way they are (sometimes for decades) or go away on their own. However, if an individual does not regularly visit a doctor regarding their AIN to be monitored and/or treated, there is the risk that they might develop into cancer.
There is no completely accurate way of determining whether someone’s AIN 2 or AIN 3 will turn into cancer, or how long this will take. Careful and frequent screening and monitoring is therefore recommended. AIN 2 and AIN 3 are most commonly caused by HPV types 16 and 18. AIN 2 and AIN 3 tend to be more common in HIV-positive individuals, although HIV-negative individuals develop them as well.
AIN 3 is considered the direct precursor to invasive squamous cell carcinoma of the anus. Studies estimate that the rate of progression from untreated AIN 3 to invasive cancer ranges from approximately 1–13% over several years, with higher rates in immunocompromised individuals. This underscores the importance of early detection and treatment.
Diagnosis
Diagnosis of AIN typically involves a combination of clinical examination and tissue biopsy. A biopsy, obtained during high-resolution anoscopy (HRA), is the definitive method for confirming a diagnosis and grading the lesion. HRA allows the clinician to apply acetic acid (vinegar) to the anal canal, which causes dysplastic tissue to turn white (acetowhitening), making abnormal areas visible under magnification before biopsy is taken. Pathological examination of the biopsy sample determines the AIN grade.
Symptoms, when present, may include anal itching, bleeding, or discomfort, though many people with AIN are entirely asymptomatic. Because AIN is frequently found incidentally during screening or evaluation of other conditions, proactive screening in at-risk populations is critical to diagnosis.
Screening
If you think you may have AIN or are at risk, it is suggested that you have a clinician screen you. Screening involves visual inspection. However, appropriate and accurate screening should also include additional methods, as a visual check alone can fail to diagnose AIN that is inside the anal canal and any subtle changes. Additional screening options include:
- Digital ano-rectal exam (DARE): a doctor places his or her fingers inside the anal canal to feel for abnormalities. The purpose of this test is to look for abnormal masses or growths, so if you think you may have precancer, request this additional testing.
- Anal Pap test: similar to a routine cervical pap test and involves sampling cells inside the anus to detect changes and abnormalities.
- Anoscopy: a tube called an anoscope is placed inside the anus and a strong light illuminates the tissue.
- High-resolution anoscopy (HRA): a more advanced anoscope with a high-resolution magnifying glass is used to examine and evaluate the tissue in the anus. This is the most precise examination for anal cancer and precancer. Learn more about HRA.
Screening Guidelines
Routine screening guidelines for anal cancer or precancer have not yet been universally adopted because there have not yet been enough studies for the government and medical communities to recommend routine screening. The predominant guidelines tend to focus on HIV-positive individuals. New York State, for example, recommends annual anal pap smears for HIV-positive men and women.
There is increasing evidence to support screening for precancers. The NIH has funded the ANCHOR study, the first randomised controlled trial for anal precancer screening efficacy and treatment.
The ANCHOR study (Anal Cancer HSIL Outcomes Research), published in the New England Journal of Medicine in 2022, found that treating HSIL (AIN 2/3) in HIV-positive individuals reduced the risk of progression to invasive anal cancer by 57% compared to active monitoring alone. This landmark finding has strengthened calls for broader, risk-stratified screening guidelines.
The International Anal Neoplasia Society (IANS) and several major HIV medicine organisations recommend anal cancer screening for high-risk groups, including HIV-positive men who have sex with men (MSM), HIV-positive women, and immunocompromised individuals such as solid organ transplant recipients. Screening intervals and modalities vary by guideline and risk group.
It is hoped that universal standards of care will be developed from ongoing research and embraced by the government and medical community.
Where Can I Get Screened?
Please see our Medical Resources page to find a clinician providing screening services in your area.
Treatment for AIN
Precancerous conditions can disappear on their own, without needing treatment. However, it is important to be frequently monitored if you are presenting with dysplasia. Even with care and treatment, recurrence is still possible, especially for individuals considered high risk, such as people living with HIV.
AIN 1 and 2
AIN 1 is generally managed conservatively with active surveillance rather than immediate intervention, given its high rate of spontaneous regression. For AIN 2, management decisions are individualised and take into account the patient’s immune status, the extent of disease, and patient preference. In immunocompetent patients with AIN 2, watchful waiting with close follow-up (typically every 6–12 months) may be appropriate. In immunocompromised patients, treatment is more often recommended. Topical therapies such as imiquimod or 5-fluorouracil (5-FU) cream may be used for both AIN 1 and AIN 2, particularly for external lesions.
AIN 3
Given its status as a direct precursor to invasive cancer, AIN 3 generally warrants active treatment rather than surveillance alone. Treatment choice depends on the size, location, and extent of disease, as well as the patient’s overall health. Options include topical therapies for small, superficial lesions, or procedural interventions such as fulguration, laser therapy, or surgical excision for more extensive disease. Regular follow-up after treatment is essential, as recurrence rates are significant, particularly in HIV-positive individuals.
Excision
Surgical excision involves the physical removal of dysplastic tissue, typically under local or general anaesthesia. It is particularly useful for well-defined, accessible lesions and allows for histological examination of the excised tissue to confirm the diagnosis and ensure clear margins. Excision may be performed as an office-based procedure for small external lesions or in a surgical setting for larger or internal lesions. There is a risk of scarring, stricture, or incontinence with more extensive excisions.
Fulguration
Fulguration (also called electrocautery or hyfrecation) uses an electrical current to destroy dysplastic tissue. It is a commonly used office-based procedure for both internal and external AIN lesions. The technique is relatively quick and well-tolerated, though it may require multiple treatment sessions for larger lesions. Post-procedure discomfort and wound healing are typical considerations.
Laser Therapy
Infrared coagulation (IRC) and CO₂ laser ablation are minimally invasive techniques used to destroy AIN lesions. IRC uses infrared light to cauterise abnormal tissue and is particularly well-suited for treating internal lesions within the anal canal. CO₂ laser offers precise tissue destruction with a controlled depth of penetration and is commonly used for both internal and external disease. Both approaches generally require local anaesthesia and may need to be repeated.
Surgery
More extensive surgical resection may be indicated in cases of widespread or recurrent high-grade AIN, or when there is concern for occult invasive cancer. Wide local excision allows for pathological assessment of the resected specimen. However, given the risk of functional complications, including anal stenosis and impaired continence, extensive surgery is typically reserved for cases where less invasive treatments have failed or where invasion cannot be excluded.
Risk Factors
Other risk factors that may increase your chances of getting anal precancer include smoking, being a transplant recipient, and being an older individual (50–80 years old). The types of changes that lead to anal precancer are also found in the cervix, vagina, vulva, and penis.
HPV
These changes are associated with infection with HPV (the human papillomavirus). AIN 1 is most commonly associated with low-risk HPV types 6 and 11, while AIN 2 and AIN 3 are most commonly caused by HPV types 16 and 18.
HPV is the most important risk factor for the development of anal dysplasia and anal cancer. HPV 16 is responsible for the majority of HPV-attributable anal cancers worldwide. Persistent infection with high-risk HPV strains — rather than transient infection — is what drives the development of high-grade precancerous lesions. HPV is transmitted through skin-to-skin contact, including sexual contact. Receptive anal intercourse is an independent risk factor for anal HPV acquisition, though HPV-related anal disease can occur in individuals with no history of anal intercourse.
HIV
AIN 2 and AIN 3 tend to be more common in HIV-positive individuals, although HIV-negative individuals develop them as well.
HIV infection significantly increases the risk of developing anal precancer and cancer. HIV impairs the immune system’s ability to clear HPV infection, leading to higher rates of HPV persistence, co-infection with multiple HPV types, and more rapid progression from low-grade to high-grade lesions. Men who have sex with men (MSM) living with HIV have among the highest rates of anal HSIL and anal cancer of any population. Even with effective antiretroviral therapy (ART), HIV-positive individuals remain at elevated risk compared to the general population, underscoring the need for regular anal cancer screening in this group.
Crohn’s Disease
Crohn’s disease, a chronic inflammatory bowel condition, is associated with an increased risk of anal and colorectal dysplasia and cancer. Perianal Crohn’s disease which causes chronic inflammation, fistulae, and scarring in the anal region creates a local environment that may promote dysplastic change. Studies have shown that individuals with longstanding perianal Crohn’s disease have a higher incidence of anal squamous cell carcinoma compared to the general population. Immunosuppressive therapies used to manage Crohn’s disease may further compound this risk. As a result, clinicians are increasingly advocating for anal cancer screening in patients with perianal Crohn’s disease.
HPV Vaccination
HPV vaccination is a key primary prevention strategy against anal precancer and cancer. The nonavalent HPV vaccine (Gardasil 9) protects against nine HPV types, including the high-risk types 16 and 18 (responsible for the majority of anal cancers) and the low-risk types 6 and 11 (which cause anal warts/AIN 1). The vaccine is most effective when administered prior to HPV exposure, ideally before sexual debut.
In the United States, the Advisory Committee on Immunization Practices (ACIP) recommends routine HPV vaccination for all individuals up to age 26, with shared clinical decision-making for those aged 27–45. Studies have demonstrated that HPV vaccination significantly reduces the incidence of anal HSIL in vaccinated populations. For individuals already diagnosed with AIN, vaccination may still be beneficial as it can provide protection against HPV types not yet acquired.
Regular screening, monitoring and rapid treatment remain the best ways to protect yourself if you think you may be at risk, alongside HPV vaccination as a preventive measure.
More Information
Learn more about anal cancer detection and prevention in this webinar from our Expert Hour series: Anal Cancer Detection and Prevention. Dr. Jessica D. Korman, a gastroenterologist at Capital Digestive Care in Washington, DC, discusses anal cancer signs and symptoms, the importance of a digital anorectal exam and high-resolution anoscopy, when a hemorrhoid is not a hemorrhoid, emerging research on anal precancer, and the HPV vaccine and its role in preventing cancer.
Peer-to-Peer Support Programme
Looking for someone to talk to about your anal cancer diagnosis? We are here to help.
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