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Anal carcinoma

  • Anal carcinoma is relatively uncommon tumour
  • The incidence appears to be increasing
  • There are 250 - 300 cases per year in England and Wales
  • They account for 4% of anorectal malignancies

Pathology

  • 80% are squamous cell carcinomas
  • Other tumour types include melanoma, lymphoma and adenocarcinoma
  • Tumour behaviour depends on its anatomical site
  • Anal margin tumours are usually well differentiated, keratinising lesions
  • They are more common in men and have a good prognosis
  • Anal canal tumours arise above the dentate line
  • They are usually poorly differentiated and non-keratinising lesions
  • They are more common in women and have a worse prognosis
  • Tumours above the dentate line spread to the pelvic lymph nodes
  • Tumours below the dentate line spread to the inguinal nodes

Aetiology

  • Anal carcinoma is more common in homosexuals
  • It is also increasingly seen in those with genital warts
  • Patients with genital warts often develop intraepithelial neoplasia
  • Intraepithelial neoplasia appears to be premalignant
  • The natural history of this premalignant state is however unknown
  • Human papilloma virus (types 16,18,31 and 33) is an important aetiological factor
  • 50% of tumours contain viral DNA

Perianal warts

Clinical features

  • 75% of tumours are initially misdiagnosed as benign lesions
  • 50% present with perianal pain and bleeding
  • Only 25% patients have identified a palpable lesion

A large ulcerating anal squamous carcinoma

Picture supplied by Mr N P J Cripps, Consultant Colorectal Surgeon, Chichester, United Kingdom

  • 70% of patients have sphincter involvement at presentation
  • This can cause faecal incontinence
  • Neglected tumours can cause a rectovaginal fistula
  • Only 50% of patients with palpable inguinal nodes have metastatic disease

Investigation

  • Rectal EUA and biopsy is the most useful 'staging' investigation
  • Endoanal ultrasound is often impossible due to pain
  • CT or MRI can be used to assess pelvic spread

Management

  • The management of anal carcinoma has changed over the last 15 years
  • Was considered a 'surgical' disease requiring radical abdominoperineal resection
  • Now most patients are managed with radiotherapy
  • The role of chemotherapy is currently undergoing investigation
  • Radiotherapy is given to tumour and inguinal nodes
  • 50% of patients respond to treatment
  • Over 5 year survival is 50%
  • Surgery is required for:
    • Tumours that fail to respond to radiotherapy
    • Large tumours causing gastrointestinal obstruction
    • Small anal margin tumours without sphincter involvement

Bibliography

Frische M,  Melbye M.  Trends in the incidence of anal carcinoma in Denmark.  Br Med J 1993;  306:  419-422.

Schofield J,  Hickson W,  Smith J et al.  Anal intraepithelial neoplasia:  part of a multifocal disease process.  Lancet 1992;  340:  1271-1273.

 

 
 

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