Expanding neoadjuvant chemotherapeutic strategies now offer patients distinct treatment options prior to surgery [1, 2]. This major shift in pre-operative care for pancreatic ductal adenocarcinoma (PDAC) has brought to light the longstanding and intricate problem concerning the accurate diagnosis of lesions in the pancreatic head. Patients with malignant (MPD) or benign (BPD) pancreaticobiliary disease often present a diagnostic challenge due to their presentation with similar symptoms, such as obstructive jaundice, as a result of a stricture in the common bile duct (CBD). Moreover, pre-operative diagnostics, including cross-sectional imaging and endoscopic ultrasound-guided fine needle biopsy, can establish a diagnosis in most patients, but some lesions can remain indeterminate [3]. Novel biomarkers are required to improve the diagnostic accuracy, ultimately leading to a decrease in unnecessary major surgeries for benign conditions. The development of reliable biomarkers that can act as adjuncts to standard clinical tests and help diagnose, and distinguish pancreaticobiliary diseases could accelerate treatment decisions and, more importantly, improve survival rates.

Currently, the only biomarker that is used to study recurrence and can support the diagnosis of PDAC is serum CA19-9 [4]. However, benign biliary obstruction with subsequent hyperbilirubinemia can also result in elevated levels of CA19-9. In recent years, microRNAs (miRNAs) have emerged as important players in tumorigenesis in different cancers, including pancreaticobiliary tumors [5]. They are a class of short RNAs that consist of approximately 18–25 non-coding nucleotides. miRNAs regulate gene expression at a post-transcriptional level, affecting protein levels and, as such, form an integral part of many biological processes. One notable feature of miRNAs is their exceptional stability across different bodily fluids like blood and bile, making them well-suited for rapid analysis [5]. Additionally, they show specific expression between tumor types, which is key in cancer biomarker discovery. To date, few studies have demonstrated the presence of miRNAs in bile [6].

Bile is in close proximity, and often in direct contact with pancreaticobiliary tumors and their microenvironment. Interestingly, bile composition is known to be involved in the development of pancreaticobiliary cancers, for example, by reducing susceptibility to apoptosis and promoting cell cycle progression [7]. It can be easily collected preoperatively during endoscopic retrograde cholangiopancreatography (ERCP) or at percutaneous transhepatic biliary drainage (PTBD) procedures for biomarker assessment. Thus, bile-based miRNAs could potentially complement the standard analysis of cytological brushings taken at ERCP or PTBD.

In this study, we aimed to identify bile-based miRNA signatures to discriminate malignant from benign pancreaticobiliary disease by global miRNA profiling of a large, prospective and multicentric cohort of bile samples.