Anus and perianal area
Carcinoma
Adenocarcinoma

Author: Raul Gonzalez, M.D. (see Authors page)

Revised: 11 October 2017, last major update October 2014

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Adenocarcinoma [title] anus "loattrfree full text"[sb]

Cite this page: Gonzalez, R. Adenocarcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/anusadenocarcinoma.html. Accessed October 19th, 2017.
Definition / general
  • Rare adenocarcinoma that primarily involves the anal canal (not rectal adenocarcinomas with downward spread)
Terminology
  • Also known as perianal adenocarcinoma or perianal gland adenocarcinoma
Epidemiology
  • 5% of anorectal malignancies
  • Usually diagnosed in the seventh decade; more common in men
Sites
  • Anus (by definition)
Pathophysiology
Etiology
Clinical features
  • May present in fistula tract or as a vaginal cyst
  • Often long history of perianal fistulas, abscesses, surgery
  • Indolent course with gradual progression
Prognostic factors
Case reports
Treatment
Clinical images

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Irregular mucosa and angioectasia

Gross description
  • Anal canal tumors are nodular, ulcerated, 3 - 4 cm or more, invade deeply into wall and spread proximally and distally into submucosa of distal rectum and proximal anus
Gross images

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Anal canal cancer

Microscopic (histologic) description
  • Haphazardly dispersed small glands with scant mucin production invading the wall of the anorectal area without an intraluminal component (Cancer 2001;92:2045)
  • Often mucinous (more than 50% of tumor volume consists of mucin); granulomatous reaction to mucin may be present
  • May contain melanin pigment, perhaps due to tumor cell phagocytosis of melanin from melanocytes (Am J Surg Pathol 1981;5:711)
Microscopic (histologic) images

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H&E, pagetoid spread

CK7, CK19

Negative staining
Differential diagnosis
  • Anal mucoepidermoid carcinoma (rare; J Gastroenterol 2001;36:508)
  • Secondary involvement by rectal adenocarcinoma (more common than primary anal adenocarcinoma; usually CK20+; may require clinical correlation)
  • Squamous cell carcinoma (far more common at this location; distinguishable microscopically)