Pancreatic fibrosis associated with age and ductal papillary hyperplasia

Little is known about the frequency, type and pathogenesis of fibrotic changes that may occur in the pancreas of persons without any clinically apparent or macroscopically visible pancreatic disease. We screened pancreas specimens for the presence and pattern of fibrosis, determined the relationship between fibrosis, age, and duct lesions, and studied the fibrogenic mechanisms. In 89 postmortem specimens from persons without any known pancreatic disease (age range 20-86 years), fibrosis was recorded and graded and the patients were divided into two age classes (younger or older than 60 years). In addition, we analyzed the association between ductal papillary hyperplasia [i.e., pancreatic intraepithelial neoplasia type 1B (PanIN-1B)] and fibrotic foci in the pancreatic tissue to determine the potential impact of obliterating duct lesions on pancreatic fibrosis. Finally, we studied the occurrence in the pancreas of myofibroblasts, identified on the basis of their alpha-SMA and desmin positivity, and determined their relationship to the fibrotic foci. Thirty-eight (44%) of 89 pancreata showed scattered foci of lobular fibrosis affecting peripheral lobuli. Fibrotic changes were significantly more common in individuals older than 60 years. Fibrotic foci were commonly associated (p<0.05) with ductal papillary hyperplasia in ducts draining fibrotic lobuli. Myofibroblasts were detected in the fibrotic foci. The "normal" pancreas develops a specific type of focally accentuated fibrosis that is highly age related. This patchy lobular fibrosis in the elderly (PLFE) was closely associated with PanIN-1B lesions in the ducts, suggesting that the narrowing of a duct due to papillary hyperplasia of the epithelium may hamper secretion and cause fibrosis of the drained lobule. The presence of myofibroblasts in association with the fibrotic foci indicates an ongoing fibrogenic process.