What is anal cancer?

Anal cancer forms in the anus, the opening at the lower end of the intestines where the end of the intestines connect to the outside of the body. As food is digested and passes through the stomach, colon, small and large intestines and rectum, waste matter is passed out of the body through the anus.  The two main groups of anal cancers include:

  • Cancers of the anal canal – start from cells in the mucosa, the lining of the canal that connects the rectum to the anus.
  • Cancers of the anal margin – form where the anal canal merges with outside skin.

More information about anal cancers (American Cancer Society)

What anal cancer is not

Anal cancer should not be confused with other gastrointestinal cancers such as colorectal, liver, pancreas, stomach neuroendocrine, or gastric and GE junction because these cancers can have different symptoms, outlooks, and treatments.

Common types of anal cancer

  • Carcinoma in situ – abnormal cells on the inner surface layer of the anus that have not spread to deeper layers.
  • Squamous cell carcinomas – the most common type of anal cancer that begins in the squamous cells lining the anal canal and margin and have spread to deeper layers.
  • Adenocarcinomas – Less common, these cancers usually start in cells that line the upper part of the anus near the rectum.


It’s possible that you could have one or more of the following tests (but not all of these will apply to your condition):

  • Imaging (CT or PET scan)
  • Lower endoscopy or colonoscopy
  • Biopsy
  • Meeting with your surgeon, medical oncologist and radiation oncologist


Depending on your unique set of conditions, your treatment could include one or more of the following treatments (but not all of these will apply to your condition):

  • Chemotherapy
  • Radiation
  • Surgery

Your full team of care providers will work closely together to review your diagnostic tests, identify the best course of treatment particular to you, and help you understand your diagnosis and what to expect with any treatment you have.