Anus & perianal area

Carcinoma

Adenocarcinoma



Topic Completed: 8 March 2021

Minor changes: 4 May 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

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

Raul S. Gonzalez, M.D.
Page views in 2020: 2,881
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Cite this page: Gonzalez RS. Adenocarcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/anusadenocarcinoma.html. Accessed November 27th, 2021.
Definition / general
  • Rare adenocarcinoma that primarily involves the anal canal (not rectal adenocarcinomas with downward spread)
Essential features
  • Rare, primary gland forming malignancy of the anus
  • May arise from anal glands, from congenital anorectal duplications or along a fistula tract
  • Must be distinguished from adenocarcinoma secondarily involving anus (e.g. rectal carcinoma)
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

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

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

Contributed by Raul S. Gonzalez, M.D.
Anal adenocarcinoma

Anal adenocarcinoma

Infiltrating glands

Infiltrating glands



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H&E, pagetoid spread

CK7, CK19

Negative staining
Sample pathology report
  • Anus, resection:
    • Anal adenocarcinoma, moderately differentiated (see synoptic report)
Differential diagnosis
Board review style question #1

Which of the following is true about primary anal adenocarcinoma?

  1. Advanced stage cases paradoxically have a better prognosis
  2. It can arise in a fistula tract
  3. It is more common in women
  4. It is more common than secondary involvement by rectal carcinoma
Board review style answer #1
B. It can arise in a fistula tract

Comment Here

Reference: Anal adenocarcinoma
Board review style question #2
Primary anal adenocarcinoma is usually positive for which of the following immunohistochemical stains?

  1. CDX2
  2. CK7
  3. CK20
  4. p16
Board review style answer #2
B. CK7. Only rare cases of anal adenocarcinoma are positive for p16.

Comment Here

Reference: Anal adenocarcinoma
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