Expression of Cytokeratins 7 and 20 in Cholangiocarcinoma and Metastatic Colonic Adenocarcinoma of the Liver

ABSTRACT

The distinction between cholangiocarcinoma (CC) and metastatic colonic adenocarcinoma of the liver (MCA) is often difficult, particularly in needle biopsy and fine-needle aspiration specimens, if histologic features alone are used. To examine the differences in the expressions of the cytokeratin (CK) 7 and 20 in the CCs and MCAs, we performed immunohistochemical studies on surgically resected 19 CCs and 23 MCAs. We used monoclonal antibodies against CK 7 and CK 20, and applied microwave antigen retrieval technique on formalin-fixed, paraffin-embedded tissue. We interpreted diffuse cytoplasmic reactivity found in > or =5% of tumor cells as positive. CCs showed CK 7+/CK 20- immunophenotype in 63%, CK 7+/CK 20+ in 32%, CK 7-/CK 20+ in 5%, and CK 7-/CK 20- in 0%. MCAs exhibited CK 7-/CK 20+ immunophenotype in 87%, CK 7+/CK 20+ in 9%, CK 7-/CK 20- in 4%, and CK 7+/CK 20- in 0%. CK 20-reactive cells in CCs were frequently columnar in shape (p<0.05). In conclusion, the CK 7/CK 20 immunophenotype was useful in the differentiation of CCs from MCAs: the CK 7+/CK 20- immunophenotype strongly suggested CCs, whereas the CK 7-/CK 20+ immunophenotype strongly suggested MCAs.