Related Subjects:
|Rectal Prolapse
|Anal Cancer
|Anal Fissure
|Perianal symptoms
|Perianal abscesses and fistulae
|Pilonidal Abscess (sinus)
|Haemorrhoids (Piles)
|Faecal Incontinence
|Rectal Pain (Proctalgia)
|Rectal Foreign Body
📖 About
- Anal cancer is rare, accounting for less than 1% of all new cancers in the UK.
- In the UK it is more common in women overall, but there are important high-risk groups, including people with HPV infection, HIV, and men who have sex with men (MSM).
- The anal canal is the terminal part of the large bowel; the dentate line marks the transition between different epithelial types and is relevant to tumour origin and management.
⚠️ Aetiology & Risk Factors
- HPV infection is the strongest risk factor; around 90% of anal cancers are linked to HPV infection, especially HPV-16.
- HIV infection increases the risk of anal cancer.
- Other recognised risk factors include smoking, immunosuppression, and previous HPV-related genital neoplasia/cancers.
- Risk is increased in MSM, particularly those living with HIV.
🩺 Clinical Presentation
- Symptoms may include rectal/anal bleeding, anal pain, itching, a lump in or around the anus, mucus discharge, or bowel incontinence.
- There may also be altered bowel habit, tenesmus, or a sensation of incomplete evacuation.
- Advanced disease may present with inguinal lymphadenopathy, ulceration, weight loss, or severe pain.
- Examination should include inspection, DRE, and palpation of the inguinal lymph nodes.
🚩 NICE referral point
- Consider a suspected cancer pathway referral for anal cancer in people with an unexplained anal mass or unexplained anal ulceration.
- Do not delay referral for FIT if there is an unexplained anal mass or ulceration.
🔎 Investigations
- Biopsy of the lesion is required for diagnosis.
- Proctoscopy/anoscopy helps define the lesion and obtain tissue.
- MRI pelvis is important for local staging.
- CT chest/abdomen/pelvis is used for metastatic staging; PET/CT may be considered in selected cases for staging or radiotherapy planning.
- Blood tests such as FBC, U&E, and LFTs are supportive baseline tests, not diagnostic tests.
- Endoanal ultrasound is not routine for all cases; MRI is usually preferred for local staging in anal canal cancer.
🧬 Pathology
- Squamous cell carcinoma (SCC) is the commonest histological type.
- Adenocarcinoma is much less common and may be managed more like a rectal cancer depending on origin and pathology.
- Other rare tumour types include melanoma, basal cell carcinoma, lymphoma, and Kaposi sarcoma.
- HPV/p16-related pathology may be reported, but histological confirmation is the key diagnostic requirement.
💊 Management
- All cases should be discussed in a specialist MDT.
- Standard treatment for most anal canal SCC is combined chemoradiotherapy.
- Common UK regimens use mitomycin with either 5-fluorouracil or capecitabine alongside radiotherapy.
- Local excision is generally reserved for selected small anal margin cancers or specific histologies, not for most anal canal SCC.
- Abdominoperineal resection (APR) is usually a salvage procedure for persistent or recurrent disease after chemoradiotherapy, or occasionally for selected tumours not suitable for organ-preserving treatment.
- Palliative treatment may include symptom-control radiotherapy, systemic therapy, stoma formation, and specialist palliative care input.
🌟 Exam Pearl: Anal squamous cell carcinoma is usually HPV-related and treated primarily with chemoradiotherapy, unlike rectal adenocarcinoma, where surgery is usually central to treatment.
📚 References
Case examples
- 🧓 Case 1 – Age 68: Six months of anal bleeding, pain, and an ulcerated anal lesion.
Investigations: Biopsy confirms squamous cell carcinoma; MRI pelvis and CT staging show no distant disease.
Management: Definitive chemoradiotherapy.
Teaching point: Most anal canal cancers are SCC and are treated with organ-preserving chemoradiotherapy rather than primary surgery.
- 🚺 Case 2 – Age 56: Small lesion at the anal margin with biopsy showing malignancy.
Management: MDT discussion determines whether this is a lesion suitable for local excision or needs chemoradiotherapy, depending on exact site, histology, and stage.
Teaching point: Anal margin and anal canal tumours are not managed identically.
- 🏳️🌈 Case 3 – Age 49: HIV-positive man with anal pain, bleeding, and an irregular anal mass.
Investigations: Histology confirms invasive SCC.
Management: Chemoradiotherapy with close specialist follow-up.
Teaching point: HIV and HPV-related disease increase anal cancer risk, but the diagnosis still depends on biopsy and staging, not risk factors alone.
