The Significance of p53 and K-ras Immunocytochemical Staining in the Diagnosis of Malignant Biliary Obstruction by Brush Cytology during ERCP

Background/Aims: Brush cytology during ERCP can provide a pathologic diagnosis in malignant biliary obstruction. K-ras and p53 mutations are commonly found in biliary and pancreatic cancers. We evaluated the diagnostic yield of brush cytology and the changes obtained by adding p53 and K-ras staining. Methods: One hundred and forty patients with biliary obstruction who underwent ERCP with brush cytology during a 7-year period were included. The sensitivity and specificity of brush cytology only and with the addition of p53 and K-ras staining were obtained. Results: Malignant biliary obstruction was confirmed in 119 patients. The sensitivity and specificity of brush cytology were 78.2% and 90.5%, respectively. The sensitivity of cytology was 77.3% at the ampulla-distal common bile duct (CBD), 92.6% at the mid common hepatic duct (CHD), and 94.7% at the proximal CBD-CHD (p＜0.05); these values did not differ with the degree or the length of the obstruction. In the 97 patients who received additional p53 and K-ras staining, the sensitivity of cytology plus p53 was 88.2%, cytology plus K-ras was 84.0%, and cytology plus p53 and K-ras was 88.2%. The sensitivity of cytology plus p53 was higher than that of brush cytology only (95% confidence interval: 83.69-92.78 vs 72.65-83.65) but not that of cytology plus K-ras. Conclusions: Brush cytology for malignant biliary obstruction has a high diagnostic accuracy. Adding p53 staining can further improve the diagnostic yield, whereas K-ras staining does not. (Gut Liver 2010;4:219-225)