The majority of anal carcinomas are keratinizing or basaloid, e.g squamous cell carcinoma. Anal adenocarcinoma is rare. Associations include chronic fistula-in-ano, anal Crohn disease, and anal sexual intercourse.

See reference 1 for details of tumor regression grading.

This case contains the complete workup including initial biopsy result, staging MR, PET/CT and CT, as well as follow up biopsy result, re-stating MR and CT.