There are several types of anal cancer: squamous cell carcinomas which develop from squamous cells-small flat cells that line the anal canal, cloacogenic carcinomas which grow between the outer part of your anus and the lower part of your rectum from cells similar to squamous cells and adenocarcinomas which develop where the anal canal meets the rectum. Here, there are squamous cells and glandular cells, which produce mucus to help faeces pass smoothly through the anus. Adenocarcinoma develops from glandular cells in the transitional zone. Cancer of the anus can also develop from the surrounding skin taking the form of either basal cell carcinoma or malignant melanoma.
Attribution: BUPA