The number staging system uses the TNM system to divide cancers into stages. Most types of cancer have 4 stages, numbered from 1 to 4.
Anal intraepithelial neoplasia means there are abnormal cells within the lining of the anus.
Stage 1 anal cancer means that the cancer is less than 2cm in size and hasn't spread to any nearby tissue, lymph nodes or other organs.
Stage 2 anal cancer is bigger than 2 cm. It hasn't spread to any nearby tissue, lymph nodes or other organs.
Stage 3 anal cancer has spread to nearby tissue or lymph nodes. It hasn't spread to distant body parts.
Stage 4 anal cancer means the cancer has spread to other parts of the body, such as the liver. It is also called advanced anal cancer.