Diagnosis of Malignant Biliary Stricture: More is Better

Biliary strictures have various etiologies. Their accurate diagnosis is still a challenge, often requiring a multidisciplinary approach. The most important differentiation is between the benign and malignant etiology. However, there is no consensus regarding an adequate diagnostic approach to malignant biliary strictures (MBS). Moreover, various etiologies of MBS may complicate the choice of diagnostic tools. In this issue of Clinical Endoscopy, Tanaka et al. report the results of a retrospective analysis of endoscopic transpapillary tissue sampling for MBS and factors predictive of diagnostic accuracy. The authors showed that a combination of forceps biopsy, brush cytology, aspiration cytology, and endoscopic nasobiliary drainage cytology improved the diagnostic accuracy of MBS, findings which are similar to those of a previous study. Major malignancies leading to MBS include pancreatic adenocarcinoma and cholangiocarcinoma. Surgical literature series show that 15%–24% of patients undergoing resection for suspected MBS based on preoperative imaging or endoscopic evaluation have a benign etiology. Thus, accurate preoperative tissue diagnosis is necessary to increase the likelihood of complete resection and to avoid perioperative morbidity and mortality. Despite multiple diagnostic methods being available, no single test has sufficient sensitivity to differentiate between benign biliary strictures and MBS. Noninvasive laboratory and radiological tests including transabdominal ultrasound, computed tomography (CT) and magnetic resonance cholangiopancreatography (MRCP) are the common initial modalities used for suspected MBS. Transabdominal ultrasound is usually the initial imaging test, but has limited ability for detection of MBS. CT can provide staging information on local spread, nodal and vascular involvement, and metastasis, and has much higher sensitivity for detection of MBS. However, CT still only has a sensitivity of 40%–77%. With a sensitivity of 96%–99% and specificity of 85% for differentiation of malignant and benign causes of obstruction, MRCP has become the preferred imaging modality in evaluation of MBS. Endoscopic retrograde cholangiopancreatography (ERCP) is the most widely used diagnostic and therapeutic modality in MBS. ERCP is useful in identifying the location and extent of MBS and acquiring specimens through brush cytology and intraductal biopsy. Endoscopic brush cytology has a sensitivity of 23%–56% and specificity of 95% in the diagnosis of MBS. Various factors can influence the poor yield of brush cytology and include both tumor characteristics and procedure-related factors. Navaneethan et al. reviewed nine studies that included 730 patients to compare the effectiveness of endoscopic brush cytology and intraductal biopsy in the diagnosis of MBS. The pooled sensitivity and specificity of brushings and intraductal biopsies was 45% and 99%, and 48.1% and 99.2%, respectively. The sensitivity and specificity can be increased to 59.4% and 100%, respectively, by combining the two methods. They showed that brushings and biopsies alone have limited Received: January 30, 2018 Revised: March 9, 2018 Accepted: March 10, 2018 Correspondence: Kwang Bum Cho Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keimyung University School of Medicine, 56 Dalseong-ro, Jung-gu, Daegu 41931, Korea Tel: +82-53-250-8096, Fax: +82-53-250-7434, E-mail: chokb@dsmc.or.kr ORCID: https://orcid.org/0000-0003-2203-102X