Histopathologic and immunohistochemical studies on the mechanism of interlobular fibrosis of the pancreas

Objective.-To elucidate the mechanism of interlobular fibrosis of the pancr eas, which is categorized as chronic alcoholic pancreatitis. Methods.-Forty pancreatic tissue samples from patients with ampullary carci nomas, which cause various degrees of stricture of the main pancreatic duct , and 20 patients with chronic alcoholic pancreatitis were studied histopat hologically and immunohistochemically. Results.-Fibrosis was observed in 23 of 40 patients with ampullary carcinom as and was classified into 3 categories: mild changes (10 cases), moderate changes (9 cases), and marked changes (4 cases). In the mild change cases; mild fibrosis was diffusely distributed in the interlobular areas, with sca nt immunoreactivity of anti-alpha-smooth muscle actin (alpha-SMA) and an ex pansive lobular appearance, whereas moderate and marked change cases showed interlobular and intralobular fibrosis with marked anti-alpha-SMA immunore activity and lobular atrophy. By quantitative analysis, the mild change cas es showed both higher MIB1-positive and lower apoptotic acinar cell ratios than those of moderate and marked changes. Anti-alpha-SMA immunoreactivity in the patients with chronic alcoholic pancreatitis was found in interlobul ar fibrosis. Hence, mild changes in cases of ampullary carcinomas had histo logic findings similar to chronic alcoholic pancreatitis, except for excess ive fibrosis cases with patchy distribution. Conclusion.-Incomplete obstruction of the main pancreatic duct caused the b eginning of interlobular fibrosis, which is categorized as chronic alcoholi c pancreatitis.