KOC (K homology domain containing protein overexpressed in cancer) and S100A4-protein immunoreactivity improves the diagnostic sensitivity of biliary brushing cytology for diagnosing pancreaticobiliary malignancies.

Biliary tract brush cytology is one of the favored methods of evaluating lesions of the pancreatobiliary tract. However, although its specificity has been reported to be high (91-100%), the sensitivity is lower (30-88%). In this study we applied KOC and S100A4 protein immunocytochemistry to assess their potential use as adjunct markers in differentiating benign from malignant cells, and improve the diagnostic sensitivity of this method for pancreatobiliary malignancies. The authors examined KOC and S100A4 protein expression in 44 alcohol-fixed cytology specimens obtained by biliary brushings. Diagnoses included: (1) benign/atypical favor reactive (20 cases), (2) atypical/not diagnostic of malignancy (3 cases), and (3) suspicious for malignancy/malignant (21 cases). Alcohol-fixed Papanicolaou-stained slides (PAP) were stained with monoclonal antibody to KOC/L523S and polyclonal antibody to S100A4 protein. Results were recorded as negative or positive. Twenty-four cases were confirmed positive for adenocarcinoma and 20 cases were negative. The sensitivity and specificity of cytology was 83 and 95%, KOC showed a sensitivity of 92% and specificity of 95%. S100A4 protein showed a sensitivity of 79% and a specificity of 95%. The combined use of KOC and S100A4 protein showed a sensitivity of 100% and a specificity of 95%, respectively. The concurrent use of KOC and S100A4 protein improves the diagnostic sensitivity of biliary brushings cytology and demonstrates similar specificity as cytology alone in the diagnosis of pancreatobiliary malignancy.