Abstract

BACKGROUND
Colonic adenocarcinoma usually shows CK7 negativity and CK20 positivity, which helps to differentiate it from cholangiocarcinoma usually showing a reverse immunohistochemical profile. We immunohistochemically investigated the pattern of CK7 and 20 expressions according to the anatomical location of colon cancer to refine the usefulness of CK expression in differential diagnosis.
METHODS
Immunohistochemical staining was done on 90 cases of surgically resected colon cancers and 84 cases of cholangiocarcinomas.
RESULTS
When the cases of colon cancer were divided into CATD (from the cecum to the descending colon) (32), sigmoid (26), and rectum (32), the positivity of CK7 was 41%, 15% and 28%, respectively, and the negativity of CK20 was 25%, 0 and 9% (p=0.013), respectively. In sigmoid colon cancers, 22 cases (85%) exhibited CK7-/CK20+ immunophenotype. However, the percentage decreased to 63% in the rectum and 47% in CATD. The CK7+/CK20- immunophenotype was found only in cancers in the cecum and ascending colon. The expression of CK7 was related to histologic differentiation (p=0.017).
CONCLUSIONS
The aberrant expressions of CKs were frequent in cancers of the rectum and ascending colon which are located in the transition site from the anus and small bowel, respectively. If adenocarcinoma in the liver were CK7+/CK20+ or CK7-/CK20-, the possibility of metastatic adenocarcinoma from CATD and rectum should be considered.

• Keywords: Colorectal Neoplasms;Cholangiocarcinoma;Keratin;Immunohistochemistry