The most common type of anal cancer is squamous cell carcinoma.
Associated with HPV infection and common in men who have sex with men and in immunosuppressed patients, especially people living with HIV.
Presenting symptoms are typically bleeding and anal pain.
The cure rate is high (75% to 90%).
Most patients are cured without a colostomy.
Standard treatment for anal cancer is fluorouracil/mitomycin plus radiotherapy, or capecitabine/mitomycin plus radiotherapy.
More intensive chemotherapy and radiation has not improved results.
Cancers of the anus can occur in three regions: the perianal skin, the anal canal, and the lower rectum. In most patients, the anal canal is 3 to 4 cm long and extends from the anal verge to the pelvic floor. The anal verge is the junction of the anal canal, where the mucosa does not contain hairs or glands, with the hair-bearing perianal skin. The anal margin extends 5 cm distal to the anal verge. A clear anatomical distinction between the anal canal and the anal margin is needed because of the different natural histories of cancers that arise in these two areas. There is considerable confusion when comparing series in the literature because of the different definitions used for the anal canal and the anal margin.
To clarify this issue, the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC) agreed that the anal canal extends from the anorectal ring to the anal verge. This is an important distinction because these two governing bodies also agreed that anal margin tumours behave in a similar fashion to skin cancers and should be classified as skin tumours and treated as such. However, if there is any involvement of the anal verge by tumour, it should be treated as an anal canal cancer.
The most common anal malignancy is squamous cell carcinoma.
Adenocarcinomas can arise from anal crypts and should be treated as a rectal cancer. Because of their location and their higher lymphatic flow compared with rectal adenocarcinomas, anal crypt adenocarcinomas have a higher risk of inguinal node spread. Squamous cell and cloacogenic histologies are collectively defined as anal canal cancers.
Other rare cancers can develop in the anal canal, including small cell neuro-endocrine carcinomas, lymphomas, and melanomas.
History and exam
Key diagnostic factors
- presence of risk factors
- rectal bleeding
- rectal pain
- rectal mass
Other diagnostic factors
- anal discharge
- anal itching
- faecal incontinence
- anal fistula
- non-healing ulcer
- inguinal node mass
- features of distant metastasis
- receptive anal intercourse
- multiple sexual partners
- autoimmune disease
- anal intraepithelial neoplasia
- anal fistula
1st investigations to order
- biopsy of tumour
- pelvic MRI scan
- pelvic CT scan
- abdominal and chest CT scan
Investigations to consider
- PET scan
- inguinal node needle biopsy
- serum HIV enzyme-linked immunosorbent assay (ELISA)
- cervical cancer screening
distant metastatic disease
- Rectal cancer
- Anal margin cancer
- NCCN clinical practice guidelines in oncology: anal carcinoma
- NCCN clinical practice guidelines in oncology: cancer in people with HIV
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