John David Horwhat, Frank G Gress
Most patients with pancreatic cancer present with a mass on radiologic studies, however, not every pancreatic mass is cancer. Since radiological studies alone are insufficient to establish the diagnosis of a pancreatic mass and patient management depends on a definitive diagnosis; confirmatory cytology or histology is usually required. As a minimally invasive procedure, EUS and EUS FNA avoid the risk of cutaneous or peritoneal contamination that may occur with CT or USguided investigations and is less invasive than surgical interventions. As a result, EUS FNA of pancreatic masses is becoming the standard for obtaining cytological diagnosis. This chapter presents an EUS-based diagnostic algorithm for the evaluation of pancreatic lesions and is based upon a review of the pertinent literature in the field of pancreatic endosonography that has been the most influential in helping to guide this evolving field. Realizing there is much overlap among the EUS characteristics of various pancreatic lesions, for the sake of simplicity we have structured our discussion in broad terms of solid versus cystic lesions and discuss various pancreatic lesions within this framework. The additional contributors to this round table discussion have been asked to provide a more dedicated, focused discussion of the various subcategories of pancreatic lesions in greater detail than we could hope to achieve here. We provide this final contribution to the round table as a means of bringing the discussion back to the big picture of pancreatic lesions, rather than trying to hone in on the fine details of any one subclass. Pancreatic cancer is one of the deadliest gastrointestinal cancers with 32,000 deaths attributed to this malignancy annually in the USA. It is the fourth leading cause of cancer death in men and women. Unfortunately, most patients with pancreatic cancer present late in the course of the disease. This explains why only 20% of patients are surgical candidates and the overall prognosis dismal with a 5-year survival rate hovering around 5%. The evaluation of pancreatic lesions suspected to be malignant could be a daunting undertaking unless one approaches the task in a focused, diligent manner. Most patients with pancreatic cancer present with a mass on radiologic studies, however, not every pancreatic mass is cancer. The differential diagnosis for a pancreatic mass on radiologic imaging includes, but is not limited to, pancreatitis, pancreatic adenocarcinoma, solid pseudopapillary tumor, neuroendocrine tumors, mucinous cystic tumors and serous cystadenoma. Since radiological studies alone are insufficient to establish the diagnosis of a pancreatic mass and patient management depends on a definitive diagnosis; confirmatory cytology or histology is usually required. Histologic diagnosis generally requires surgical intervention, an invasive procedure that may not be needed for patients who have benign disease or who have advanced cancer. On the other hand, a cytological diagnosis can be obtained utilizing minimally invasive methods, including a radiological- (CT or US) guided, endoscopic ultrasound-guided (EUS), or laparoscopic-guided approach. CT/USguided fine needle aspiration (FNA) carries the risk of cutaneous or peritoneal seeding and laparoscopy needs to be performed in an operating room setting and is more invasive than CT or EUS. Since EUS is a minimally invasive procedure and EUS-guided FNA avoids the risk of cutaneous or peritoneal contamination, EUS-guided FNA of pancreatic masses is becoming the standard for obtaining cytological diagnosis. In this chapter, we present an EUS-based diagnostic algorithm for the evaluation of pancreatic lesions (Figures 1 and 2). As we take the reader through the algorithm, we will discuss the pertinent literature in the field of pancreatic endosonography (EUS) that has been the most influential in helping to design this algorithm.
