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Anal canal

Extends from the opening of the anus to the internal anal sphincter about 4 cm in length: the lowest 2 cm is cutaneous tissue and the upper 2 cm is covered by mucosa.

A rare disease that accounts for less than 1% and 3% of all new cancer diagnoses and gastrointestinal tumors, respectively.

Extends from the perianal skin (the anal verge) to the rectal mucosa.

The dentate line represents the end of the squamous mucosa and the beginning of the zone of transition from squamous to nonsquamous mucosa.

Tumors can be keratinizing or nonkeratizing depending on the location in relation to the dentate line.

The most common histological subtype squamous cell carcinoma with an annual incidence of 0.5 to 2.0 in 100,000.

The incidence is increasing.

The five year overall survival has increased.

Keratinizing and nonkeratizing cancers have similar biology and prognosis.

Consists of a sphincter muscle complex at the level of the puborectalis muscle, multiple types of mucosa with sensory nerves, anal glands and vascular hemorrhoidal channels.

squamous cell carcinoma of the anus and its precursor lesion, anal intraepithelial neoplasia are mostly attributable to human papillomavirus infection, which represents the causative agent in 80-85% of patients.

HPV 16 and HPV 18 are the major subtypes.

Anal intercourse in a high lifetime number of sexual partners increases the risk of persistent HPV infection leading to malignancy.

additional important risk factors include HIV infection, prior history of anogenital warts, lower genital tract malignancies, immuno suppression in transplant recipients, history of HPV related other cancers, autoimmune disorders and cigarette smoking.

Patients may present with bleeding and diagnosis may be delayed because bleeding is attributed to hemorrhoids.

Clinically anal cancer may present with a mass, a nonhealing ulcer, pain, bleeding, itching, discharge, fecal incontinence and fistula.

Digital anal rectal examination is essential for clinical diagnosis.

The diagnosis is made by biopsy proven histology.

 

HPV vaccination is expected to result in lower incidence of anal carcinoma.

Primary tumor assessment is done by MRI exam, however CT scan seven thorax abdomen and pelvis may be required to assess potential metastatic disease sites.

Patients with HPV positive tumors have improved disease free survival as compared with patients with HPV negative disease.

Patients with skin ulceration, nodal involvement and male sex have increased risk for a local regional failure.

Patients must be evaluated for the HIV status.

 

 

 

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