[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Anal cancer

[Conditions](https://durgical.com/en/conditions/) · [Hematology and oncology](https://durgical.com/en/conditions/)

# Anal cancer

Cancer of the [anal canal](https://durgical.com/en/anatomy/anal-canal/), nearly always caused by HPV. It often looks like haemorrhoids at first and is usually curable with chemotherapy and radiation.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Anal canal](https://durgical.com/en/anatomy/anal-canal/)
- [External anal sphincter](https://durgical.com/en/anatomy/external-anal-sphincter/)
- [Rectum](https://durgical.com/en/anatomy/rectum/)
- [Perineal body](https://durgical.com/en/anatomy/perineal-body/)
- [Superficial inguinal nodes](https://durgical.com/en/anatomy/superficial-inguinal-nodes/)

## Why it happens

- [Oncogenic viruses and H. pylori: the table to know](https://durgical.com/en/general-pathology/oncogenic-viruses-and-h-pylori-the-table-to-know/)
- [Dysplasia and carcinoma in situ](https://durgical.com/en/general-pathology/dysplasia-and-carcinoma-in-situ/)

## What it is

A malignant tumour of the anal canal or perianal skin, in most cases a squamous cell carcinoma caused by persistent infection with high-risk human papillomavirus (HPV). Unlike rectal cancer, the standard treatment is chemoradiotherapy rather than surgery.

## Who gets it

Uncommon in the general population, but incidence is rising, especially in women over 50 and in people living with HIV. Men who have sex with men with HIV have the highest risk. In Colombia, HPV is also the cause of cervical cancer, a leading cancer in women, and HPV vaccination of girls in the national programme is expected to lower anal cancer too.

## Causes

- Persistent high-risk HPV infection, especially types 16 and 18 (about 90–95% of cases)
- Progression through anal intraepithelial neoplasia (high-grade squamous intraepithelial lesion, HSIL)
- Rare histologies: adenocarcinoma, melanoma

## Risk factors

- HIV infection, especially with low CD4 counts
- Receptive anal intercourse and many sexual partners
- Previous cervical, vulvar or vaginal HPV-related lesions or cancer
- Solid organ transplant and other immunosuppression
- Smoking
- Anogenital warts

## Pathophysiology

High-risk HPV infects basal cells at the anal transformation zone, where the columnar rectal lining meets squamous anal skin, the same kind of junction found in the [cervix](https://durgical.com/en/anatomy/cervix-of-uterus/). Viral E6 and E7 proteins inactivate p53 and retinoblastoma protein, allowing uncontrolled growth. Weak immunity, particularly in HIV, lets the virus persist and lesions progress from low-grade to high-grade dysplasia and then invasive cancer. Tumours of the upper canal drain to perirectal and pelvic nodes; those below the dentate line drain to the inguinal nodes.

## Classification

- Anal canal versus perianal (anal margin) tumours
- Squamous cell carcinoma (most) versus adenocarcinoma and others
- AJCC TNM stage based on tumour size, nodes and distant spread
- Precursor: high-grade squamous intraepithelial lesion

## Symptoms and signs

- Bright red bleeding from the anus, the most common symptom
- Anal pain, itching or a feeling of a lump
- A mass or ulcer at the anal margin
- Change in bowel habit or faecal incontinence in advanced disease
- Swollen inguinal lymph nodes
- Up to a fifth of patients have no symptoms

## Red flags

- Anal bleeding or a lump that does not settle with haemorrhoid treatment, especially in a person with HIV
- A hard, ulcerated or fixed anal lesion
- Faecal incontinence or fistula into the [vagina](https://durgical.com/en/anatomy/vagina/)
- Enlarged hard inguinal nodes

## Diagnosis

**Clinical**
Inspection of the perianal [skin](https://durgical.com/en/anatomy/skin/), digital rectal examination and palpation of the inguinal nodes; bleeding is too often blamed on haemorrhoids without an examination. In women, a gynaecological examination looks for other HPV lesions.

**Tests**
Anoscopy with biopsy of the lesion confirms the diagnosis; fine-needle aspiration or biopsy of enlarged inguinal nodes; HIV testing. In high-risk groups, anal cytology and high-resolution anoscopy detect precursor lesions.

**Imaging**
Pelvic MRI for local staging; CT of the [chest](https://durgical.com/en/anatomy/region/chest/) and [abdomen](https://durgical.com/en/anatomy/region/abdomen/) or PET-CT for nodes and distant spread; endoanal ultrasound in some centres.

## Differential diagnosis

- Haemorrhoids
- Anal fissure
- Perianal abscess or fistula, including Crohn disease
- Condylomata acuminata (anogenital warts)
- Rectal adenocarcinoma invading the anal canal
- Syphilitic chancre

## Goal of treatment

Cure the cancer while keeping the anal sphincter, with surgery kept for small lesions or for disease left after chemoradiotherapy.

## Treatment

**Medical**
Definitive chemoradiotherapy, with fluorouracil or capecitabine plus mitomycin given alongside pelvic radiotherapy, is standard for stages I–III and preserves the sphincter in most patients.

**Surgical**
Local excision for small, well-differentiated perianal tumours and for precancerous lesions; abdominoperineal resection with permanent colostomy is reserved for residual or recurrent disease after chemoradiotherapy.

**Medical**
Platinum-based chemotherapy and immune checkpoint inhibitors for metastatic disease; antiretroviral therapy continued in people with HIV.

**Follow-up**
Response is judged by examination several weeks to months after treatment, because tumours keep shrinking; regular digital rectal examination, anoscopy and imaging follow. Nursing care manages perineal skin reactions to radiation, pain, diarrhoea, low blood counts and stoma care when needed.

## Complications

- Faecal incontinence and stenosis
- Radiation dermatitis, proctitis and bowel or bladder damage
- Sexual dysfunction and infertility after pelvic radiotherapy
- Neutropenia from chemotherapy
- Local recurrence and spread to inguinal nodes, [liver](https://durgical.com/en/anatomy/liver/) and lungs

## Prognosis

Usually curable: five-year survival exceeds 85% for early disease and is still above half for many node-positive cases without distant spread. Tumour size and nodal status are the main prognostic factors.

## Prevention

- HPV vaccination before the start of sexual activity
- Condom use (partial protection)
- Not smoking
- Screening for anal precancer in people with HIV and other high-risk groups where available

## Test yourself

Think of the answer, then tap the question to see it.

## What is the main cause of anal squamous cell carcinoma?

Persistent high-risk HPV infection, mostly types 16 and 18.

## What is the standard first treatment for localised anal canal cancer?

Chemoradiotherapy with fluorouracil (or capecitabine) and mitomycin, which spares the sphincter.

## When is abdominoperineal resection used in anal cancer?

As salvage for tumour left or returning after chemoradiotherapy.

## To which lymph nodes do tumours below the dentate line drain?

The superficial inguinal lymph nodes.

## Which group has the highest risk of anal cancer?

People living with HIV, especially men who have sex with men.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/conditions/anal-cancer/)

## Related conditions

- [Human papillomavirus (HPV) infection](https://durgical.com/en/conditions/human-papillomavirus-infection/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)
- [Viral warts (verruca)](https://durgical.com/en/conditions/viral-warts/)
- [Cervical cancer](https://durgical.com/en/conditions/cervical-cancer/)
- [Haemorrhoids](https://durgical.com/en/conditions/haemorrhoids/)
- [Anal fissure](https://durgical.com/en/conditions/anal-fissure/)
- [Anorectal abscess and fistula](https://durgical.com/en/conditions/anorectal-abscess-and-fistula/)
- [Crohn disease](https://durgical.com/en/conditions/crohn-disease/)
- [Colorectal cancer](https://durgical.com/en/conditions/colorectal-cancer/)
- [Lower gastrointestinal bleeding](https://durgical.com/en/conditions/lower-gastrointestinal-bleeding/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Anal Cancer Treatment (PDQ®)–Health Professional Version](https://www.cancer.gov/types/anal/hp/anal-treatment-pdq) (National Cancer Institute, 2025).

[← All conditions](https://durgical.com/en/conditions/)

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/conditions/anal-cancer/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/anal-cancer/