Abstract
Making a tissue diagnosis of pancreatic adenocarcinoma is best accomplished by EUS and fine-needle aspiration (FNA) of the lesion. Typically, a dark, or "hypoechoic" mass will be seen, which presents an obvious target for FNA. For small lesions, computerized tomography (CT) may be negative, but the lesion is still almost always seen on EUS imaging. Rarely, a pancreatic mass will appear isoechoic on EUS imaging. We report three "invisible" pancreatic masses identified only by a cutoff in the pancreatic duct (PD) and/or common bile duct (CBD). No mass, isoechoic or otherwise, was seen. EUS-FNA was performed in the area of ductal narrowing, with a positive identification of adenocarcinoma in these cases.