Anus & perianal area
Carcinoma
Adenocarcinoma
Author: Raul S. Gonzalez, M.D.
Topic Completed: 1 October 2014
Minor changes: 16 November 2020
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Adenocarcinoma [title] anus "loattrfree full text"[sb]
Table of Contents
Definition / general | 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 | Differential diagnosis | Additional referencesCite this page: Gonzalez RS. Adenocarcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/anusadenocarcinoma.html. Accessed January 22nd, 2021.
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
- 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)
Etiology
- Proposed etiologic associations include chronic fistula, anal Crohn 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
Images hosted on other servers:
H&E, pagetoid spread
CK7, CK19
Positive stains
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)
