The Pathology of Anal Neoplasia

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The Pathology of Anal Neoplasia

• Dr Bryan F Warren
• Consultant Gastrointestinal Pathologist, Honorary
  Senior Lecturer and Fellow of Linacre College,
• Oxford
• M62 Course 2005

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Epithelial tumours of the anus

• Rare and diverse in histological type.
• many different types of epithelium present.
• malignant tumours anal canal and anal margin.
• Anal margin tumours-keratinising squamous cell
  carcinomas with better prognosis and need less
  aggressive treatment than their non-keratinising
  variants in the anal canal.

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Benign tumours of the anus

• fibro epithelial polyps,
• inflammatory cloacogenic polyps
• squamous hyperplasia (leucoplakia).
• Anal intraepithelial neoplasia (AIN).

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AIN (Dysplasia of the squamous epithelium of the
anal canal)

• AIN 1, 2 or 3 depending on its severity
• precursor of squamous cell carcinoma
• related to human papilloma virus.
• Interobserver variation in the diagnosis of AIN
  1, 2 and 3. 44.6 44.7 44.8 44.9 44.10
• .

AIN 111
AIN 1 and wart virus effects
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Viral warts

• Viral warts may also be seen at the anal verge -
  condylomata acuminata
• Giant condyloma of Buschke and Loewenstein which
  may be enormous before it develops invasion. The
  invasion is by veruccous carcinoma which may
  present considerable difficulties in diagnosis on
  biopsy, since the cytology is so bland.

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Benign anal lesions which may mimic malignancy

• .
• Keratoacanthoma - benign lesion which can be
  misdiagnosed as SCC
• Bowens Disease - SCC in situ.
• Cf Bowenoid papulosis is a papular eruption in
  the anogenital region in young to middle aged
  adults and the histology resembles Bowens
  Disease. This can cause considerable confusion
  if viewed histologically in isolation without the
  history and knowledge of the macroscopic
  appearances of this eruption around the anus and
  this may lead to misdiagnosis with serious
  consequences.

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Uncommon tumours

• Sweat gland tumours,
• Extramammary Pagets disease,
• (Metastatic tumours occasionally)

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Malignant epithelial tumours

• squamous cell carcinoma, which in the anal canal
  is often basaloid or non-keratinising,
• malignant melanoma, which unfortunately usually
  presents quite late due to the site
• Anal gland tumours

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Malignant melanoma

• Malignant melanoma, unfortunately usually
  presents quite late due to the site

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Anal gland adenocarcinoma

• Adenocarcinoma of anal ducts and anal glands.
  colloid carcinoma causes considerable
  difficulties biopsies - mucus only (endoscopic
  appearances are characteristic).
• Mucinous adenocarcinomas may occur within
  fistulae.

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Anal gland adenocarcinoma
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Anal margin tumours - skin tumours

• Anal margin squamous cell carcinomas and basal
  cell carcinomas may be seen other very rare
  tumours may occur occasionally

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Pathological staging of anal canal carcinoma

• Tx cannot be assessed
• T0 no evidence of primary tumour
• Tis carcinoma in situ
• T1Tumour /lt 2 cm
• T2 Tumour 2-5cm
• T3 Tumour gt 5cm
• T4 Tumour invades adjacent organs (vagina,
  urethra, bladder - invasion of sphincter
  muscle(s) alone does not make it T4)

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Pathological staging of anal canal carcinoma

• Regional lymph nodes perirectal, internal iliac,
  inguinal lymph nodes.
• Nx cannot be assessed
• N0 No regional lymph node metastasis
• N1 Metastasis in perirectal lymph nodes
• N2 Metastasis in unilateral internal iliac and /
  or inguinal lymph node(s)
• N3 Metastasis in perirectal and inguinal lymph
  nodes and / or bilateral internal iliac and / or
  inguinal lymph nodes

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Pathological staging of anal canal carcinoma

• Mx,M0,M1
• UICC stages
• Stage 0 Tis N0M0
• Stage I T1 N0M0
• Stage II T2/3 N0M0
• Stage IIIA T1,2,3 N1M0 or T4N0M0
• Stage IIIB T4N1M0, or any T withN2,N3M0
• Stage IV Any TorN with M1

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Summary

• Correct pathological diagnosis of anal neoplasia
  is crucial to the correct management.

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