What is anal cancer?
Cells in the anal canal or perianal skin sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous, or benign, conditions such as anal warts, polyps or skin tags.
Changes to cells in the anal region can also cause a precancerous condition called anal intraepithelial neoplasia (AIN). This means that the cells are not yet cancer, but there is a chance that they may become cancer if they aren’t treated.
In some cases, changes to cells in the anal canal or perianal skin can cause cancer. Anal cancer usually starts in round, flat cells called squamous cells. These cells are inside the anal canal and make up the perianal skin. This type of cancer is called squamous cell carcinoma of the anus.
Rare types of anal cancer can also develop. These include adenocarcinoma, basal cell carcinoma, melanoma and gastrointestinal stromal tumour (GIST).
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