RESUMO
BACKGROUND: Pathologists occasionally have difficulty in distinguishing cholangiocarcinoma from benign reactive cells on the biliary cytology. We estimated the diagnostic value of insulinlike growth factor II mRNA binding protein 3 (IMP3) on biliary cytology specimens. METHODS: We selected 40 patients who had undergone a biliary cytology examination and whose diagnoses were confirmed by biopsy. The IMP3 expression was evaluated by immunohistochemical staining in both the tissue and the cytology specimens. Their histologic diagnoses were cholangiocarcinoma (n = 34), high grade dysplasia (n = 2), low grade dysplasia (n = 1) and non-biliary tumor or no tumor (n = 3). RESULTS: On the histology, all the cases of cholangiocarcinoma or high grade dysplasia were positive for IMP3 (36/36). The low grade dysplasia or the normal bile ducts in the other 4 cases were negative for IMP3 (0/4). Of the 36 cases diagnosed as cholangiocarcinoma or high grade dysplasia histologically, 29 cases were positive for IMP3 on the cytology (29/36; sensitivity, 80.6%). Of the 4 cases without cholangiocarcinoma or high grade dysplasia, 1 case was weakly positive for IMP3 on the cytology. The histologic diagnosis of this case was hepatocellular carcinoma. Except for this hepatocellular carcinoma case, the specificity of IMP3 on the cytology was 100%. CONCLUSIONS: IMP3 is a useful diagnostic marker for cholangiocarcinoma on cytology.