Expression of integrin aVb6 differentiates perihilar cholangiocarcinoma from benign disease mimicking PHC

Background: Approximately 15% of patients undergoing resection for presumed perihilar cholangiocarcinoma (PHC) have benign disease at final pathological assessment. Molecular imaging targeting tumor-specific biomarkers could serve as a novel diagnostic tool to reduce these futile surgeries. Imaging agents have been developed, selectively binding integrin α _νβ _6, a cell receptor upregulated in pancreatobiliary malignancies, for both (preoperative) PET and (intraoperative) fluorescent imaging. Here, expression of integrin α _νβ ₆ is evaluated in PHC, intrahepatic cholangiocarcinoma (ICC), hepatocellular carcinoma (HCC) and benign disease mimicking PHC using immunohistochemistry. Materials & methods: Three tissue microarrays (TMA) including 103 PHC tumor cores and sixty tissue samples were selected from resection specimens of pathologically proven PHC (n = 20), ICC (n = 10), HCC (n = 10), metastatic PHC lymph nodes (n = 10) and benign disease (presumed PHC with benign disease at pathological assessment, n = 10). These samples were stained for integrin α _νβ ₆ and quantified using the H-score. Results: Immunohistochemical staining for integrin α _νβ ₆ showed membranous expression in all twenty PHC whole mount slides (100%) and 93 out of 103 (92%) PHC tumor cores. Mean H-score of PHC samples was 195 ± 71, compared to a mean H-score of 126 ± 57 in benign samples (p = 0.013). In both benign and PHC samples, inflammatory infiltrates and pre-existent peribiliary glands showed integrin α _νβ ₆ expression. The mean H-score across ten ICC was 33 ± 53, which was significantly lower compared to PHC (p < 0.001) but too weak to consistently discriminate ICC from HCC (H-score 0)(p = 0.062). Conclusion: Integrin α _νβ ₆ is abundantly expressed in PHC and associated metastatic lymph nodes. Expression is significantly higher in PHC as compared to benign disease mimicking PHC, ICC and HCC, emphasizing its potential as a target for tumor-specific molecular imaging.