Additional p53 and K-ras Immunohistochemical Stain Can Not Enhance the Outcome of Brush Cytology During ERCP

Abstract

Background and aims: Brush cytology at obstructed biliary tree during ERCP is the standard method for getting the tissue diagnosis in malignant biliary obstruction. K-ras and p53 mutation are common and early molecular events in biliary and pancreas cancer. We evaluate the outcome of brush cytology and study whether additional p53 and k-ras immunohistochemical (IHC) stain can enhance the outcome of brush cytology. Patients and Method: In 97 patients with biliary obstruction, we evaluate if the presence of 3-D cluster of cells on smeared slide, site of bushing (ampulla and distal CBD, mid CBD, proximal CBD), tightness of biliary obstruction (tight, intermediate, loose), and length of obstruction (=< 2 cm, >2 cm) can influence the result of brush cytology. In addition we did IHC stain for p53 and k-ras with brush cytology slides in 64 patients with biliary obstruction. Results: Among 97 patients with biliary obstruction, 78 obstructions was malignant stricture by final diagnosis after surgery and long-term follow up. For malignant biliary obstruction, the sensitivity and specificity of brush cytology during ERCP at stricture were 89.7% and 98.6% respectively. 3-D cluster was more common in malignant obstruction than benign obstruction {68/86 (79.1%) vs. 9/17 (52.9%), p < 0.05}. There were no differences in the sensitivities of brush cytology according to the level of obstruction in CBD, tightness of obstruction, and the length of obstruction. In 64 patients done additional p53 and k-ras IHC stain, sensitivity of brush cytology plus p53 in malignant obstruction was 96.8%, that of brush cytology plus k-ras was 93.7%, that of brush cytology plus p53 and k-ras was 98.4%. But there was no difference in sensitivity on adding p53 or k-ras IHC stain. Conclusion: The diagnostic accuracy of brush cytology at biliary obstruction during ERCP was very high, and 3D-cluster of cells on slide was more common in malignant obstruction. Additional p53 and k-ras IHC stain can not enhance the outcome of brush cytology.