Anus & perianal area
Carcinoma
Adenocarcinoma
Author: Raul S. Gonzalez, M.D.
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]
Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Prognostic factors | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative staining | Sample pathology report | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Gonzalez RS. Adenocarcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/anusadenocarcinoma.html. Accessed July 24th, 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
- May arise from anal glands, from congenital anorectal duplications or along a fistula tract (Dis Colon Rectum 1998;41:992)
- May demonstrate HPV 18 DNA but not HPV 16 DNA (Mod Pathol 1991;4:58)
- Accordingly, rare cases are linked to HPV infection and are positive for p16 (Mod Pathol 2020;33:944)
Etiology
- Proposed etiologic associations include chronic fistula, anal Crohn's disease and anal sexual intercourse (Semin Surg Oncol 1994;10:235)
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
- Poor prognosis associated with advanced T and N category disease and higher histologic grade (Int J Radiat Oncol Biol Phys 2003;56:1274)
Case reports
- 84 year old man with adenocarcinoma arising from an anal gland (Int J Surg Case Rep 2014;5:234)
Treatment
- Standard treatment includes abdominoperineal resection; adding chemotherapy and radiation improves outcome (Int J Radiat Oncol Biol Phys 2003;56:1274)
Clinical images
Images hosted on other servers:
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
Images hosted on other servers:
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
Infiltrating glands
Images hosted on other servers:
H&E, pagetoid spread
CK7, CK19
Positive stains
Negative staining
- CK20, CDX2, usually p16 (Arch Pathol Lab Med 2007;131:1304)
Sample pathology report
- Anus, resection:
- Anal adenocarcinoma, moderately differentiated (see synoptic report)
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
Additional references
Board review style question #1
Which of the following is true about primary anal adenocarcinoma?
- Advanced stage cases paradoxically have a better prognosis
- It can arise in a fistula tract
- It is more common in women
- It is more common than secondary involvement by rectal carcinoma
Board review style answer #1
Board review style question #2
Primary anal adenocarcinoma is usually positive for which of the following immunohistochemical stains?
- CDX2
- CK7
- CK20
- p16
Board review style answer #2
B. CK7. Only rare cases of anal adenocarcinoma are positive for p16.
Comment Here
Reference: Anal adenocarcinoma
Comment Here
Reference: Anal adenocarcinoma
