Adenocarcinoma of the Anus
Definition
- Adenocarcinoma arising in the anal canal or in adjacent deep tissues
Alternate/Historical names:
- Perianal adenocarcinoma (for extra-mucosal adenocarcinoma)
- Perianal gland adenocarcinoma (for extra-mucosal adenocarcinoma)
Diagnostic Criteria
- Must primarily involve the anal canal
- Carcinomas extending down from the rectum are considered rectal adenocarcinomas
- Two basic types of anal adenocarcinoma
- Colorectal type
- Originates in mucosa
- May have a residual mucosal lesion
- Histologically identical to colorectal adenocarcinoma
- Originates in mucosa
- Extra-mucosal, fistula / anal gland type
- No overlying mucosal lesion
- May ulcerate
- Most cases associated with chronic anorectal fistula
- May be associated with Crohn disease
- Most cases are mucinous
- >50% of tumor volume is mucin
- Ductal / tubular differentiation may be seen
- No overlying mucosal lesion
- Colorectal type
- Paget disease may be present
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates : 10/7/10, 11/13/11
