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.

• Keywords: Cholangiocarcinoma;Metastatic colonic adenocarcinoma;Cytokeratin 7;Cytokeratin 20