Endoscopic ultrasound (EUS) is the most sensitive imaging modality for solid pancreatic lesions. The specificity, however, is low (about 75%). It can be increased to 100% with an accuracy of 95% by the addition of fine-needle aspiration (FNA). Cytopathology plays an important role. The final diagnosis is based upon the correlation of clinical, EUS, and cytologic features. A close interaction with the cytopathologist is required in improving the diagnostic yield. In this paper, we present an overview of the role of EUS-guided FNA and importance of close interaction with the cytopathologist. Day to day examples of different solid pancreatic lesions have been presented at the end. 1. Introduction Endoscopic ultrasound (EUS) is an emerging imaging modality. EUS-guided fine-needle aspiration (FNA) plays an important role in solid pancreatic lesions. A close interaction with cytopathology is vital in improving the diagnostic yield. The final diagnosis is based upon correlation of clinical, EUS, and cytologic features. In this paper, we will discuss the role of EUS-FNA, and the importance of cytopathology in the diagnosis of solid pancreatic lesions. We will describe the history and safety of EUS, indications for an EUS-FNA, and a short description of the technique of EUS-FNA. We will also discuss the importance of arranging an onsite cytopathologist and alternatives if that is not feasible. Finally, we will present the clinical, EUS, and key cytologic features of a few representative solid pancreatic lesions. 2. Endoscopic Ultrasound (EUS): Background Endoscopic ultrasound (EUS) was first introduced by Dr. Eugene DiMagno in the 1980s by combining a high-frequency ultrasound transducer to an endoscope [1]. Initial echoendoscopes were radial, which scan perpendicular to scope’s axis and provide 360-degree images similar to computerized tomography (CT) (Figure 1). In 1991, convex linear-array echoendoscope was introduced by Pentax (FG-32). These linear scopes scan parallel to the longitudinal axis of the scope and enable fine needle aspiration (FNA) and different therapeutic applications (Figure 2). Figure 1: Radial echoendoscope. The tip of the scope scans perpendicular to its axis, providing 360-degree view. Figure 2: Linear echoendoscope. The tip scans parallel to its longitudinal axis. An FNA needle is seen coming out of the scope channel. Different imaging modalities are available to help diagnose solid pancreatic lesions including transabdominal ultrasound, computerized tomography (CT), magnetic resonance imaging (MRI), endoscopic retrograde
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