Anus & perianal area
Carcinoma
Carcinoma overview
Author: Raul S. Gonzalez, M.D.
Editorial Board Member: Xiaoyan Liao, M.D., Ph.D.
Deputy Editor-in-Chief: Aaron R. Huber, D.O.
Last author update: 22 April 2025
Last staff update: 22 April 2025
Copyright: 2002-2025, PathologyOutlines.com, Inc.
PubMed Search: Anus carcinoma
Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Sites | Pathophysiology | Clinical features | Diagnosis | Prognostic factors | Treatment | Differential diagnosis | Additional references | Practice question #1 | Practice answer #1 | Practice question #2 | Practice answer #2Cite this page: Gonzalez RS. Carcinoma overview. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/anuscarcinomageneral.html. Accessed September 10th, 2025.
Definition / general
- Carcinoma arising in anus, usually of squamous origin (more than 80% of cases)
- WHO classification includes squamous cell carcinoma, verrucous carcinoma, adenocarcinoma, neuroendocrine tumor and neuroendocrine carcinoma
Essential features
- Most anal carcinomas are squamous, with human papillomavirus (HPV) as a risk factor
- Most common in middle aged women
- Human immunodeficiency virus (HIV) positive men who have sex with men are at high risk
Terminology
- Perhaps more accurately called anal canal carcinoma
- Per WHO: anal canal tumor "cannot be seen in its entirety, or at all, when gentle traction is placed on the buttocks" but perianal tumor "is found within a 5 cm radius of the anus and is seen completely when gentle traction is placed on the anus"
ICD coding
Epidemiology
- Uncommon (1 - 2% of GI tumors)
- More common in women (2 - 4:1); average age at diagnosis is early 60s
- Rising incidence in the past 40 years (Oncologist 2007;12:524, Eur J Cancer Prev 2024;33:77)
- American Cancer Society estimates for 2024: 10,540 cases and 2,190 deaths in the United States (American Cancer Society: Anal Cancer [Accessed 2 April 2025])
- Neuroendocrine carcinomas and especially neuroendocrine tumors are rare at this location
Sites
- The lesions in this overview occur in the anal canal
- Neoplasms can also occur in the perianal skin, such as basal cell carcinoma
Pathophysiology
- Most anal squamous carcinomas are linked to infection with human papillomavirus 16 or 18 (Mod Pathol 1996;9:614, Mod Pathol 1989;2:439)
- Therefore, HPV vaccination may lead to decreased incidence (J Low Genit Tract Dis 2013;17:397)
- Other risk factors include HIV infection, smoking, male receptive anal intercourse (Ann Intern Med 2008;148:728, N Engl J Med 1987;317:973)
- Highest incidence rate is among HIV positive men who have sex with men (Curr Oncol 2023;30:3232)
- Extramammary Paget disease may occur in the anus, either primary or secondary to an anal adenocarcinoma
Clinical features
- Symptoms include rectal / anal bleeding, anal pain or itching, change in bowel habits, feeling of a mass at anal opening
Diagnosis
- Annual screening of at risk populations using anal Pap smear appears effective (JAMA 1999;281:1822)
- Imaging is useful for staging (Curr Oncol 2023;30:3232)
- Carcinoma staging uses the AJCC system
Prognostic factors
- 5 year survival rate is 83% for localized T1 / T2 cancers, compared with 36% for stage 4 cancers (American Cancer Society: Anal Cancer Survival Rates [Accessed 2 April 2025])
- Lymph node involvement is a poor prognostic factor (Ann Surg Oncol 2007;14:478)
Treatment
- Surgery alone for small lesions; advanced tumors may also require chemoradiation (5-fluorouracil / mitomycin) (Curr Oncol Rep 2009;11:186)
Differential diagnosis
- Rectal carcinoma:
- Depending on subtype, may be difficult to distinguish from anal adenocarcinoma or (less likely) anal squamous cell carcinoma
Additional references
Practice question #1
What is the most common primary tumor of the anus?
- Adenocarcinoma
- Basal cell carcinoma
- Neuroendocrine carcinoma
- Squamous cell carcinoma
Practice answer #1
D. Squamous cell carcinoma is the most common primary tumor of the anus. Answers A and C are incorrect because they are rare forms of anal malignancy. Answer B is incorrect because basal cell carcinoma arises in perianal skin, not the anal canal.
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Reference: Carcinoma overview
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Reference: Carcinoma overview
Practice question #2
What screening method can be used for patients at high risk of anal carcinoma?
- Annual anal Pap smear
- Annual colonoscopy
- Annual computed tomography (CT) scan
- Annual magnetic resonance imaging (MRI) scan
Practice answer #2
A. Annual anal Pap smear can be used to screen patients at high risk for anal malignancy. Answers B, C and D are incorrect because these modalities are not used to screen this patient population.
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Reference: Carcinoma overview
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Reference: Carcinoma overview
