Optimal tissue sampling during ERCP and emerging molecular techniques for the differentiation of benign and malignant biliary strictures

Abstract

Patients with cholangiocarcinoma have poor survival since the majority of patients are diagnosed at a stage precluding surgical resection, due to locally irresectable tumors and/or metastases. Optimization of diagnostic strategies, with a principal role for tissue diagnosis, is essential to detect cancers at an earlier stage amenable to curative treatment. Current barriers for a tissue diagnosis include both insufficient tissue sampling and a difficult cyto- or histopathological assessment. During endoscopic retrograde cholangiopancreatography, optimal brush sampling includes obtaining more than one brush within an individual patient to increase its diagnostic value. Currently, no significant increase of the diagnostic accuracy for the new cytology brush devices aiming to enhance the cellularity of brushings versus standard biliary brush devices has been demonstrated. Peroral cholangioscopy with bile duct biopsies appears to be a valuable tool in the diagnostic work-up of indeterminate biliary strictures, and may overcome current technical difficulties of fluoroscopic-guided biopsies. Over the past years, molecular techniques to detect chromosomal instability, mutations and methylation profiling of tumors have revolutionized, and implementation of these techniques on biliary tissue during diagnostic work-up of biliary strictures may be awaited in the near future. Fluorescence in situ hybridization has already been implemented in routine diagnostic evaluation of biliary strictures in several centers. Next-generation sequencing is promising for standard diagnostic care in biliary strictures, and recent studies have shown adequate detection of prevalent genomic alterations in KRAS, TP53, CDKN2A, SMAD4, PIK3CA, and GNAS on biliary brush material. Detection of DNA methylation of tumor suppressor genes and microRNAs may evolve over the coming years to a valuable diagnostic tool for cholangiocarcinoma. This review summarizes optimal strategies for biliary tissue sampling during endoscopic retrograde cholangiopancreatography and focuses on the evolving molecular techniques on biliary tissue to improve the differentiation of benign and malignant biliary strictures.

Keywords: chromosomal imbalance; epigenetics; immunohistochemistry; mutation; next-generation sequencing.

Figure 1.

Examples of routine cytology of biliary brush samples. (a) Normal biliary epithelial cells. (b) Atypia; reactive changes with variation in nuclear size, often observed in PSC. (c) Adenocarcinoma, showing variation in nuclear architecture and size. Papanicolaou staining. Original magnification, ×25. PSC, primary sclerosing cholangitis.

Figure 2.

Examples of FISH negative (a) and positive (b) cases for MYC copy-number assessment. (a) Tumor cells with two signals for each of the two probes. (b) Tumor cells with MYC amplification. MYC (green); centromere-bounded probe (red).