Immunohistochemical Staining Improves the Diagnostic Yield of Bile Duct Biopsies

Abstract

Differentiation of malignant versus benign biliary strictures can be challenging. Histological evaluation of endoscopic biopsies is highly specific, but can lack sensitivity. The aim of our study was to evaluate the utility of immunohistochemical staining of biliary biopsies in the diagnosis of malignant strictures. Methods: 22 cases of biliary strictures were retrospectively reviewed. Biliary biopsy specimens were obtained during routine endoscopic retrograde cholangiopacreatograms. Final diagnoses were established from clinical follow-up or by direct evaluation of surgical specimens. 13 benign and 9 malignant strictures were identified. Benign etiologies included gallstones and chronic pancreatitis; malignancies were 7 cholangiocarcinomas and 2 invasive pancreatic adenocarcinomas. Immunohistochemical staining for p53, M1B, CAM5.2, CEA, CA19-9, and Alcian blue/PAS, alone or in combination were analyzed. For the purpose of this study, atypical samples were considered to be benign. Findings: Histology alone had sensitivity of 55% and specificity of 100% in detection of malignancy. Alcian-blue/PAS stain had the best sensitivity of 64% with specificity of 93%. In one case with final malignant diagnosis Alcian-blue/PAS stain was positive whereas histology was deemed benign. P53 stain had sensitivity and specificity of 55% and 87%, respectively. Addition of p53 stain to histology increased the sensitivity to 64% with specificity of 87% with one case of malignancy staining positive for p53 with negative histology. CAM5.2 stain had sensitivity of 42% with specificity of 100%. Though the specificity of CA19-9 was relatively high at 80%, sensitivity was low at 18%. Both the M1B and CEA increased sensitivity to 74%, but had relatively low specificity of 53% each. Addition of all 6 immunohistochemical markers increased the sensitivity to 82% but decreased specificity to 20%. Conclusion: Addition of immunohistochemical staining to histology can improve diagnostic yield of bile duct biopsies. Alcian-blue/PAS and p53 each offered the best combination of sensitivity and specificity.