IMP3 immunocytochemical staining increases sensitivity in the routine cytologic evaluation of biliary brush specimens.

Biliary brush cytology is an important diagnostic tool in the evaluation of biliary strictures. Here, we evaluated 64 patients with biliary strictures who underwent endoscopic retrograde cholangiopancreatography with bile duct brushings. We assessed the utility of combining routine Papanicolaou-stained cytologic evaluation with immunocytochemical expression of insulin-like growth factor mRNA-binding protein-3 (IMP3). Definitive diagnoses were obtained via tissue resection/autopsy, biopsy, fine needle aspiration, or clinical progression of disease. Thirty-nine of the 64 patients were ultimately diagnosed with malignancy. The sensitivity of routine cytology for the detection of malignancy was 33.3%, immunocytochemical-IMP3 expression was 64.1%, and the combined sensitivity was 71.8%. The specificity of each method was 100%. The sensitivity of IMP3 immunocytochemical staining in the detection of malignancy in biliary brushings was superior to routine PAP-stained cytologic evaluation. Moreover, the combined use of biliary brushing cytology and IMP3 immunohistochemistry proved superior to the use of either method alone.