Normal Components and Contaminants.

The pancreas is a retroperitoneal organ located in the duodenal loop with the posterior wall of the stomach overlying it and the left lobe of the liver lying anteriorly to it. Tissues from these organs, in addition to the lesion of interest within the pancreas, may be sampled during fine-needle aspiration (FNA) procedures. Therefore, it is important to recognize the cytology of normal benign components of the pancreas and potential contaminants in order to render a correct diagnosis and avoid pitfalls. Normal components of the pancreas include ductal epithelial cells, acinar cells, and islet cells. In addition to the normal pancreatic cells, it is not uncommon to encounter epithelial cells from the duodenal and gastric mucosa with endoscopic ultrasound-guided fine-needle aspiration. It is important to recognize these cells as benign and to distinguish them from a well-differentiated pancreatic adenocarcinoma. Besides these, mesothelial cells and hepatocytes and bile duct cells from the liver may be sampled as well. Here, the cytological features of normal components and contaminants are described in detail.