Number stages of anal cancer
AIN means there are abnormal cells in the lining of the anus.
AIN may not cause any symptoms. But if it does, they can include:
your anus being itchy
bleeding or passing from your anus
pain in your anus
The symptoms of AIN can be caused by other conditions such as piles (haemorrhoids). But they can also be caused by anal cancer, so it is important to see your doctor if you have any of these symptoms.
Research suggests that AIN is linked to the human papilloma virus (HPV).
This is a common infection that gets passed from one person to another by sexual contact. For most people the virus causes no harm and goes away without treatment. There are many different types of HPV, most are harmless. But some can increase the risk of AIN if they remain in the body.
Your doctor checks for AIN by looking at your anus and taking a sample of tissue. They call this an anoscopy and biopsy.
A specialist doctor called a pathologist looks at the biopsy under a microscope. They can see if any of the cells are abnormal. And if they are, how abnormal they are. This is called the grade of the AIN. Whether you need treatment or not depends on the grade.
Find out more about having an anoscopy and biopsy
AIN can be divided into 3 grades. These are numbered 1 to 3:
AIN 1 – the cells are slightly abnormal
AIN 2 - the cells are moderately abnormal
AIN 3 - the cells are severely abnormal
Or doctors refer to AIN as a low grade or high grade squamous epithelial lesion (SIL). This is because most of the abnormal cells are a type of cell called .
Low grade SIL (LSIL) means the cells are slightly different to normal anal cells. LSIL is the same as AIN 1.
High grade SIL (HSIL) means the cells are moderately to severely different from normal anal cells. HSIL is the same as AIN 2 and AIN 3.
Low grade SIL can go away on its own so you may not need treatment. Your doctor may arrange regular follow ups to check the SIL for any changes. Or they might suggest you get retested at a later date. This is to check if the cells have gone back to normal.
But for some people treatment can relieve symptoms such as burning, itching, and bleeding. Your doctor will talk to you about your treatment options.
You will need treatment because the abnormal cells are less likely to get better on their own. They might develop into anal cancer, but the risk of this is very small. Your doctor will discuss the best treatment option for you. Treatments might include:
skin creams such as imiquimod or 5FU
destroying the cells using heat or laser (ablation)
trichloroacetic acid – a liquid which your doctor or nurse puts directly on the SIL
Less often people may have surgery to remove the SIL.
These treatments are also used for different types of cancers. You can find out more about the treatments on our treatment pages. But remember AIN is not cancer.
Read more about some of these treatments
Unfortunately in a small number of people, high grade lesions can develop into anal cancer.
How big an anal cancer is and whether it has spread is called the stage of the cancer. Treatment depends on the stage but includes and surgery.
Finding out you have abnormal cells in the anus can be worrying.
For support and information, you can call the Cancer Research UK information nurses. They can give advice about who can help you and what kind of support is available. Freephone: 0808 800 4040 - Monday to Friday, 9am to 5pm.
Last reviewed: 23 Jun 2025
Next review due: 23 Jun 2028
You can’t catch cancer, but some infections such as HPV can increase your risk. Learn about how infections can cause cancer here.
HPV is a common infection. For most people, it doesn't cause problems but some types can increase cancer risk.
Anal cancer symptoms may include bleeding, bowel changes and severe itching around the anus (pruritus). It is important to see your doctor if you have any of these symptoms.
Treatments can include surgery, radiotherapy and drug treatments (such as chemotherapy, hormone therapy or targeted cancer drugs). Find out about treatments and how to cope with side effects.
Anal cancer is when abnormal cells in the anus divide in an uncontrolled way. It can start in different parts of the anus and different types of cell.
