The distribution of fibrosis mostly corresponds to or is based on individual causes, as shown in table 1. Pancreatic fibrosis or chronic pancreatitis due to pancreatic duct obstruction is known as chronic obstructive pancreatitis (COP), which is characterized by both inter- and intralobular fibrosis and lobular/acinar atrophy. Autoimmune pancreatitis (AIP), recently a focus of attention, shows a similar fibrosis pattern to COP, except that it is accompanied by marked lymphoplasmacytic infiltration . Fibrosis due to biliary diseases such as gallstones or choledochal cysts is distributed in the interlobular and periductal areas . Fibrosis after acute pancreatitis includes surrounding areas of both necrosis and lobules; the latter is called perilobular fibrosis . Fibrosis in hemochromatosis or severe hemosiderosis is found in diffuse intralobular and periinsular areas . However, as for chronic alcohol abuse, which is the most common cause of pancreatic fibrosis, it remains unclear, in terms of the fibrosis pattern, whether all types of pancreatic fibrosis in chronic alcohol abuse patients can be categorized as chronic alcoholic pancreatitis. According to Martin , there are at least three types of fibroatrophic states found in the pancreas: (1) Predominantly intralobular sclerosis (IS), which is always homogenous and diffuse (fig. 1); (2) predominantly perilobular sclerosis (PS), which presents with a 'cirrhosis-like' appearance but is irregular and sometimes patchy (fig. 2), and (3) mixed IS and PS (MS), which is often homogeneously distributed in the pancreas (fig. 3). According to our previous study , the pancreatic fibrosis associated with alcohol abuse can show any of Martin's
Table 2. Distribution of types of pancreatic fibrosis in chronic alcohol abuse (94 cases) and clinically diagnosed chronic alcoholic pancreatitis (30 cases)
Cases Pancreatic Predominantly Predominantly Mixed fibrosis intralobular perilobular intralobular and sclerosis sclerosis perilobular sclerosis
Alcohol abuse 94 50 16 17 17
Chronic alcoholic 30 30 0 30 0
*Clinically diagnosed cases.
classification patterns, and chronic alcoholic pancreatitis can be identified by the presence of predominantly perilobular sclerosis, while alcoholic dependence syndrome mainly shows predominantly intralobular and mixed intralobular and perilobular sclerosis, as shown in table 2. Moreover, we think that MS should be included in the IS category, because fibrosis of the MS type is seen mainly in the intralobular or periacinar areas and is uniformly distributed.
Based on the distribution of fibrosis, perilobular, interlobular, or intralobular, and the difference in various components and accompanying diseases such as liver cirrhosis, pancreatic fibrosis can be classified into two distinct pathogenic entities which occur via different mechanisms . Therefore, pancreatic fibrosis can be classified into interlobular and intralobular types; the former is identified with chronic alcoholic pancreatitis, while the latter should be designated as so-called pancreatic fibrosis.
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