Accurate diagnosis of strictures involving the bile duct is essential to the planning of therapy and the choice of the right treatment option, such as surgical resection or endoscopic stenting. However, differentiation of malignant from benign ductal lesions at endoscopic retrograde cholangiopancreatography (ERCP) remains a challenge. Although cholangiographic features may be characteristic for malignant or benign disease, in many cases histological or cytological proof of the diagnosis is required to determine the optimal treatment for each individual patient. Histological and cytological tissue diagnoses may be obtained by several methods, including open biopsy, ultrasound or computed tomography guided fine needle aspiration or core biopsy, endoscopic forceps biopsy, endoscopic brush cytology, and bile aspiration cytology.^1–4

Brush cytology performed at ERCP has become the preferred initial method of pursuing tissue diagnosis in many patients with pancreatobiliary strictures.^5–9 The technique allows easy and convenient sampling and has a low complication rate.^3,9,10 The diagnostic specificity of biliary brush cytology is very high and few false positive diagnoses have been reported. The major limitation of the technique has been the relatively modest diagnostic sensitivity. The sensitivity rates reported in multiple studies are highly variable and range between 30% and 88%, with nearly 100% specificity.^3,4,9–12 In general, results of brush cytology for biliary strictures induced by pancreatic malignancies have proved to be inferior (on average 46%) to those observed for biliary malignancies (on average 68%).⁴

The success rate of brush cytology analyses is largely dependent on two factors: (1) the quality of the cytological material obtained at ERCP and (2) the expertise of the cytopathologist.

The quality of the cytological material is influenced by the processing technique, cellularity, cellular preservation, background, quantity …