CD56-positive Cells with or without Synaptophysin Expression are Recognized in the Pancreatic Duct Epithelium: A Study with Adult and Fetal Tissues and Specimens from Chronic Pancreatitis

We observed the distribution of CD56+ epithelial cells in the pancreatic duct system using 25 fetal, one infantile, 3 normal adult, 4 diabetic, and 8 chronically inflamed pancreatic tissue samples. In the early stage of gestation (12 to 17 weeks), CD56+ cells were commonly seen in the immature tubular structures. They were often continuous to pancreatic islets, and their distribution was similar to that of synaptophysin (Syn)+ cells, suggesting that they are precursors of islet neogenesis. Their number decreased in proportion to gestational age. Instead, from 24 weeks of gestation, luminal cell clusters that were common in interlobular ducts revealed CD56+. These cell clusters were unrelated to islet neogenesis and Syn expression. Similar CD56+ luminal cell clusters were also observed in cases of chronic pancreatitis, whereas they were scarce in normal adult and diabetic tissues. CD56+ cells were also occasionally seen in intralobular ducts, intercalated ducts, and centroacinar cells in cases of chronic pancreatitis. We conclude that there are two types of CD56+ epithelial cells in the pancreatic duct system: CD56+ endocrine cells are numerous during the early stage of gestation, when islet neogenesis appears, while CD56+ luminal cells may represent developmental and regenerative changes of pancreatic ducts.