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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.

Carcinogenesis of primary sclerosing cholangitis (PSC)-associated cholangiocarcinoma (CCA) is largely unexplored. Improved understanding of the molecular events involved may guide development of novel avenues for rational clinical management. We aimed to assess the genetic alterations during progression of the neoplastic cascade from biliary dysplasia towards CCA in PSC. Forty-four resection specimens or biopsies of PSC patients with biliary dysplasia (n = 2) and/or CCA (n = 42) were included. DNA was extracted from sections of formalin-fixed paraffin-embedded tissue blocks with dysplasia (n = 23), CCA (n = 69), and nonneoplastic tissue (n = 28). A custom-made nextgeneration sequencing (NGS) panel of 28 genes was used for mutation and copy number variation (CNV) detection. In addition, CNVs of CDKN2A, EGFR, MCL1, and MYC were examined by fluorescence in situ hybridization. Alterations in 16 low-grade dysplasia samples included loss of FGFR1 (19%), CDKN2A (13%), and SMAD4 (6%), amplification of FGFR3 (6%), EGFR (6%), and ERBB2 (6%), and mutations in SMAD4 (13%). High-grade dysplasia (n = 7) is characterized by MYC amplification (43%), and mutations in ERBB2 (71%) and TP53 (86%). TP53 mutations are the most common aberrations in PSC-CCA (30%), whereas mutations in KRAS (16%), GNAS (14%), and PIK3CA (9%) are also common. In conclusion, PSC-CCA exhibits a variety of genetic alterations during progression of the neoplastic cascade, with mainly CNVs being present early, whereas mutations in ERBB2, TP53, and KRAS appear later in the development of CCA. These findings are promising for the development of NGS-guided diagnostic strategies in PSC-CCA.

INTRODUCTION: Intertumor and intratumor heterogeneity may explain the diagnostic challenge and limited efficacy of chemotherapy for primary sclerosing cholangitis–associated cholangiocarcinoma (PSC-CCA). In this study, tumor heterogeneity was assessed through p53 and p16 protein expression analysis and next-generation sequencing (NGS) of TP53 and CDKN2A genetic alterations in PSC-associated CCA. METHODS: Formalin-fixed paraffin-embedded tissue samples from resection material of patients with PSC-CCA or patients with PSC diagnosed with biliary dysplasia were selected. Sections with CCA and foci with dysplastic epithelium were identified by 2 independent gastrointestinal pathologists. Immunohistochemical evaluation of p53 and p16 protein expression and NGS of TP53 and CDKN2A genetic alterations were performed. RESULTS: A total of 49 CCA and 21 dysplasia samples were identified in the resection specimens of 26 patients. P53 protein expression showed loss of expression, wild type, and overexpression in 14%, 63%, and 23% CCA and in 19%, 62%, and 19% dysplasia samples, respectively. P16 protein expression showed negative, heterogeneous, and positive results in 31%, 57%, and 12% CCA and in 33%, 53%, and 14% dysplasia samples, respectively. NGS showed high intertumor and intratumor heterogeneity of TP53 mutations and CDKN2A loss. Nearly 70% of the samples with a TP53 missense mutation demonstrated p53 overexpression, whereas all samples with a TP53 nonsense mutation demonstrated loss of p53 protein expression. DISCUSSION: PSC-associated CCA is characterized by high intertumor and intratumor heterogeneity of both p53/p16 protein expression and genetic alterations in TP53 / CDKN2A , indicating that these tumors consist of multiple subclones with substantially different genetic makeup. The high intertumor and intratumor heterogeneity in PSC-CCA should be acknowledged during the development of diagnostic and therapeutic strategies.