Anal gland carcinoma.

BACKGROUND

Anal gland carcinoma is a rare entity. The authors conducted a joint study of cases coded as definite or possible anal gland carcinoma from the archives of the Armed Forces Institute of Pathology and the Canadian Reference Center for Cancer Pathology.

METHODS

Seven cases of potential anal gland carcinoma were identified from the Canadian files and 12 from the Armed Forces Institute of Pathology archives. Of these 19 cases, 14 had adequate material to allow clinical, histologic, and immunohistochemical analysis.

RESULTS

Seven of these 14 cases met a modified World Health Organization (WHO) definition of anal gland carcinoma. The mean age of these patients was 66 years (range, 60-72 years), with a male-to-female ratio of 6:1. The tumors were composed of haphazardly dispersed, small glands with scant mucin production that invaded the wall of the anorectal area with no obvious intraluminal component observed clinically or microscopically. Immunohistochemical studies were performed on all seven of these cases, revealing cytokeratin (CK) 7+/CK 20- expression in six cases, and CK 7+/CK 20+ expression in one case. The remaining seven cases showed no intraluminal component but did not meet a modified WHO definition of anal gland carcinoma. This group included three mucinous adenocarcinomas (two clinically arising in anal fistulas), all of which were CK 7+/CK 20+, and a rectal-type adenocarcinoma that was CK 7-/CK 20+. There was also a tumor interpreted as probable rectal-type adenocarcinoma that was CK 7+/CK 20+, and a tumor interpreted as probable squamous cell carcinoma that was CK 7-/CK 20-. The seventh tumor in this group, which could not be classified, was CK 7+/CK 20-.

CONCLUSIONS

A useful and discriminating definition of anal gland carcinoma is an anal canal tumor composed of haphazardly dispersed, small glands with scant mucin production invading the wall of the anorectal area without an intraluminal component. The glands are positive for CK 7.