Anal Cancer Workup

Updated: Sep 25, 2018
  • Author: Thomas R Dekoj, MD; Chief Editor: N Joseph Espat, MD, MS, FACS  more...
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Workup

Approach Considerations

Anal cancer is typically found in one of the following three ways:

  • As an incidental finding on biopsy for another reason
  • During surveillance for anal intraepithelial neoplasia (AIN; precancerous lesion)
  • Discovered de novo

Anoscopy and rigid proctoscopy to determine the size of the primary lesion and the extent of the spread of disease will guide preoperative staging. Incisional or punch biopsy of the lesion as well as core needle biopsy of suspected lymph node spread should also be performed. Pap smear testing of the anus and cervix can be performed to document the presence of high-risk serotypes of human papillomavirus (HPV). [26]

A biopsy result is the first step in the diagnostic algorithm. Rarely, the biopsy will reveal entities other than squamous cell carcinoma, such as the following:

When biopsy identifies an entity other than squamous cell carcinoma, the subsequent workup will mirror more closely the workup of disease from that entity at other sites in the body.

In patients with anal squamous cell carcinoma, colonoscopy examination is also recommended, as there is a 15% incidence of colorectal neoplasm discovered at the time of diagnosis, though there is no known link between colorectal cancer and anal cancer [26] .

Imaging studies for all anal cancer patients should include a computed tomography (CT) scan of the chest, abdomen, and pelvis to evaluate for enlarged lymph nodes and metastatic spread. Female patients should be evaluated with a thorough gynecologic examination, including screening for cervical cancer. A positron emission tomography (PET)–CT scan can be considered in certain clinical scenarios. HIV testing may be appropriate and is advocated by many authorities, with a CD4 level when indicated. [26, 27]

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Screening

Currently, no major regulatory or professional body recommends anal cancer screening for the general population, and controversy surrounds the questions of which patients are candidates for screening and what techniques should be used. Colorectal cancer screening in any form except colonoscopy has little to no likelihood of discovering anal cancer, though a digital rectal examination should be performed when a screening test is ordered or performed. Anal cancer may be discovered during colonoscopy or during the pre-procedure digital rectal examination, but the screening protocols designed for the discovery of colorectal cancer are not designed to discover anal cancer.

In general, screening is recommended in patients at high risk for anal cancer, such as the following:

  • Some immunocompromised patients (eg, kidney or liver transplant recipients)
  • Patients with anogenital warts
  • HIV-positive men who have sex with men (MSM)

The HIV Medicine Association of the Infectious Diseases Society of America (IDSA) recommends screening by anal Papanicolaou (Pap) smear for the following HIV-positive patients [28, 29] :

  • MSM
  • Women with a history of receptive anal intercourse or abnormal cervical Pap smear
  • HIV-positive people with anogenital warts 

Possible screening methods for anal cancer and AIN include the following:

  • Anal Pap smear
  • High-resolution anoscopy (HRA)
  • Digital anorectal examination
  • HPV testing

HRA serves as the gold standard of anal cancer screening. However, it is perhaps prohibitively expensive and poorly implementable. [30]

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Staging

Staging is based on the widely used American Joint Committee on Cancer (AJCC) tumor-node-metastasis (TNM) system, to stratify patients into research, treatment, and survival groupings. [11] The primary tumor classification is based on size and depth of invasion, nodal status is based on location of the nodes, and metastatic disease is designated as present (M1) or absent (M0).

Primary tumor (T) designations are as follows:

  • Tis - High-grade squamous intraepithelial lesion (previously termed carcinoma in situ, Bowen disease, anal intraepithelial neoplasia II–III, high-grade anal intraepithelial neoplasia)
  • T1 - Tumor ≤ 2 cm
  • T2 - Tumor  2–5 cm
  • T3 - Tumor > 5 cm
  • T4 - Any size tumor that invades adjacent organs (eg, vagina, bladder, urethra, but not anal sphincter complex)

Regional lymph node designations are as follows:

  • N0 - No regional lymph node metastasis
  • N1 - Metastasis in inguinal, mesorectal, internal iliac, or external iliac nodes
  • N1a - Metastasis in inguinal, mesorectal, or internal iliac, lymph nodes
  • N1b - Metastasis in external iliac lymph nodes
  • N1c - Metastasis in external iliac with any N1a nodes

Metastasis designations are as follows:

  • M0 - No distant metastasis
  • M1 - Distant metastasis

Anatomic stage/prognostic groups are listed in the Table below.

Table. Anatomic stage/prognostic group (Open Table in a new window)

Stage

T

N

M

0

Tis N0 M0
I T1 N0 M0
IIA T2 N0 M0
IIB T3 N0 M0
IIIA T1-2 N1 M0
IIIB T4 N0 M0
IIIC T3-4 N1 M0
IV Any T Any N M1

See also Anal Cancer Staging.

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