AJCC has defined 3 anatomic regions in which anal or perianal squamous cell cancer may be manifested
anal canal lesions: cannot be visualized or are incompletely visualized by gentle traction of the buttocks
perianal lesions: completely visible and arise within 5 cm of the anal opening when the buttocks are gently spread
skin lesions: arise outside of the 5-cm radius and are treated like skin lesions in any other site of the body
there can be overlap between anal canal lesions and perianal lesions
Lymphatic Drainage
spreads through 3 different sets of regional nodes
superiorly, above the dentate line, lymph vessels follow the superior hemorrhoidal artery and terminate in the preaortic
and paraaortic nodes
laterally, the drainage follows the middle hemorrhoidal vessels to the internal iliac nodes
inferiorly, below the dentate line, the drainage follows the inferior hemorrhoidal vessels and terminates
in the inguinal nodes
Anal Canal Neoplasms
Squamous Cell Cancer
arises from the anal transition zone
strongly associated with HPV infection
occurs more commonly in women, and women should be screened for cervical cancer
other risk factors include receptive anal intercourse, HIV, immunosuppression, smoking
Diagnosis
patients may have only minor symptoms and are often misdiagnosed as having benign anorectal
disorders (hemorrhoids, anal fissure)
perianal pain, bleeding, and an indurated mass on exam should suggest the diagnosis of anal cancer
rectal examination reveals the size, location, and degree of fixation of the tumor
anoscopy verifies the exact location of the tumor relative to the dentate line
the mass should be biopsied for histologic diagnosis
examination of both inguinal regions determines if there is any suspicious nodal enlargement
staging includes CT of the chest, abdomen, and pelvis, and pelvic MRI
Therapy
Chemoradiation
now the standard treatment
5-year survival rates are as high as 92% in node-negative patients
combines external beam radiation (at least 45Gy) with a continuous infusion of 5-FU
and a bolus injection of Mitomycin-C
Abdominoperineal Resection
standard treatment prior to 1974
5-year survival ranged from 50% to 70%
local recurrence rates in the pelvis ranged from 25% to 50%
additional morbidities include nonhealing of the perineal wound, sexual dysfunction,
and a permanent colostomy
now reserved as salvage therapy after failed chemoradiation or recurrent disease
Management of the Inguinal nodes
sentinel node biopsy can improve lymph node staging, but its value is unclear since
the inguinal lymph nodes are routinely included in the radiation field
superficial and deep inguinal node dissection is reserved for patients with bulky nodal
disease or recurrent nodal disease after irradiation
Melanoma
3rd most common site for melanoma (skin, eye)
frequently amelanotic
often mistaken for a thrombosed hemorrhoid
has a poor prognosis, with 5-year survival rates < 10%
does not respond to chemoradiation
if an R0 resection can be performed with a wide local excision, this is preferred over an APR,
since extent of resection does not improve survival
Adenocarcinoma
usually is a distal extension of a low rectal cancer
rarely may arise from the columnar epithelium of the anal glands or from a chronic anal fistula
most patients are treated with multimodality therapy – chemoradiation and APR
Anal Margin Tumors
Condyloma Acuminatum
caused by sexually transmitted HPV virus
considered a premalignant lesion
more common in immunocompromised patients
Clinical Presentation
pruritus, bleeding, pain, discharge, palpable mass
exam reveals pinkish warts that may coalesce to form a mass
anoscopy may reveal disease within the anal canal
high-resolution anoscopy with or without 5% acetic acid may improve detection of disease
perineum and genitals must also be carefully inspected for disease
HIV testing should be done
sexual partners should be contacted and evaluated
Treatment
no consensus on a gold-standard treatment
recurrence rates are between 20% - 50% irrespective of treatment approach
