Genetic alterations of pancreatic intraductal lesions adjacent to invasive ductal carcinoma were investigated. We submitted nine foci of ordinary epithelium, 12 foci of nonpapillary hyperplasia, 12 foci of papillary hyperplasia (pap HP), 66 foci of severe ductal dysplasia, and 27 invasive foci from a total of 10 pancreatic carcinomas for genetic analysis. All foci were individually microdissected and allelic losses of 3p, 4q, 5q, 6q, 8p, 9p, 10q, 11q, 13q, 16q, 17p, and 18q were studied. All invasive and severely dysplastic intraductal foci exhibited loss of heterozygosity (LOH) at more than one chromosomal locus. For each case, allelic loss was frequently observed on 9p (severe ductal dysplasia 90%, invasion 100%), 17p (severe ductal dysplasia 80%, invasion 80%), and 18q (severe ductal dysplasia 88%, invasion 88%). Ninetyfour percent of severe ductal dysplasia and 96% of invasive foci had multiple LOH. Seventeen percent of nonpapillary hyperplasia and 33% of pap HP showed LOH. Only one focus of pap HP showed multiple LOH. The patterns of allelic loss identified in severe ductal dysplasia were generally conserved in synchronous infiltrating tumors, supporting the paradigm that infiltrating tumors are clonally derived from severe ductal dysplasia. In eight of 10 cases, however, we found frequent genetic heterogeneity in the intraductal lesion, suggestive of genetic progression or diversion. These findings indicate that invasive pancreatic carcinoma evolves through successive and divergent genetic changes with selection of aggressive subclones in the intraductal component. Pancreatic ductal carcinoma carries a very poor prognosis because early detection is difficult and effective treatment is not established. The mortality rate of pancreatic carcinoma has been increasing recently in eastern Europe, North America, and in Japan.1,2 A molecular understanding of pancreatic tumorigenesis is critical for developing efficient detection methods and treatment protocols. Molecular studies of pancreatic carcinoma have advanced recently. The oncogene K-ras mutation has been described as its earliest genetic change.3-8 A number of tumor suppressor genes, such as p53, p16, and DPC4, have also been found to play a critical role in the clonal progression of pancreatic tumorigenesis. 9 -20 Using frozen tissue, cell lines, and xenografts, invasive pancreatic carcinoma has been found to have allelic loss on many chromosomal arms.9,21-25 Among these, 1p, 9p, 17p, and 18q have been reported to be deleted in more than 60% of cases, followed by 3p, 6p, 6q, 8p, 10q, 12q, 13q, 21q, and 22q, which have been reported to be deleted in 40 to 60% of pancreatic carcinomas. These chromosomal loci may harbor unidentified tumor suppressor genes critical to the development of pancreatic carcinoma.A diverse spectrum of intraductal epithelial changes, ie, nonpapillary hyperplasia (non-pap HP), papillary hyperplasia (pap HP), atypical hyperplasia/severe dysplasia, and so forth, has been described around invasive pancreatic carcinomas. Mucous cell h...

Paneth cells in the following species were observed under an electron microscope: human, rhesus monkey, hare, guinea pig, rat, nude rat, mouse, golden hamster, and insect feeder bat. Secretory granules containing homogeneous electron-dense materials were observed in the Paneth cells of humans, monkeys, hares, guinea pigs, and bats; mouse Paneth-cell granules were bipartite (central core and peripheral halo), and the Paneth cells in rats and golden hamsters had secretory granules showing various electron densities. In humans, monkeys, and bats, immature granules near the Golgi apparatus sometimes showed bipartite substructure. The number and size of secretory granules were also diverse among various animal species. Some lysosome-like bodies were commonly observed in peri- or supranuclear regions, though the size and shape of the bodies differed from cell to cell. In apical cytoplasm, small clear vesicles (100-200 nm diameter) were more-or-less observed in all species examined, and it was especially note that rat Paneth cells contained many clear vesicles. Small dense-cored vesicles (150-200 nm diameter) were rare. It is unlikely that the various ultrastructural features of Paneth cells correlate with the phylogenetical classification.

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To confirm whether the Paneth cells of mice (ICR, male, 10-12 weeks old) have the same secretory response to hormonal and cholinergic stimulation as do pancreatic acinar cells, ultrastructural changes of Paneth cells and pancreatic acinar cells 1 hr after administration of various doses of cholecystokinin (octapeptide, CCK-8) and carbamylcholine were morphometrically assessed. After maximal (1.5 micrograms/kg intraperitoneally [i.p.]) and supramaximal (15 micrograms/kg, i.p.) stimulation by CCK-8, pancreatic acinar cells showed, respectively, degranulation or disturbance of secretion (e.g., an increase in lysosome-like bodies, aggregation of zymogen granules). The Paneth cells, however, were almost unchanged in the parameters examined. After carbamylcholine injection (1,000 micrograms/kg, subcutaneously [s.c.]), both pancreatic acinar cells and Paneth cells showed degranulation. Paneth cells sometimes developed large vacuoles, probably formed after massive exocytosis; such vacuoles were not observed in pancreatic acinar cells. It is suggested that Paneth cells and pancreatic acinar cells have different secretory responses. Paneth cell secretion, which possibly plays a role in controlling the intestinal bacterial milieu, may be stimulated by cholinergic rather than hormonal mechanisms.

Mucous cell hyperplasia (MCH) has been considered an important precursor of pancreatic ductal carcinoma based on histological and molecular research, although various K‐ras mutations rates are seen among cases with pancreatic carcinoma, chronic pancreatitis and normal pancreas, with a wide range of histological characters. To investigate the premalignant potential of MCH and the multicentricity of pancreatic carcinoma, we analyzed K‐ras mutation at codon 12 in carcinoma foci of 82 cases of surgically‐resected pancreatic carcinoma [67 solid‐type carcinomas (SCs) and 15 ductectatic‐type carcinomas (DCs)], as well as in both MCH and carcinoma foci in 42 cases (30 SCs and 12 DCs), using an enriched polymerase chain reaction (PCR)‐enzyme linked mini‐sequence assay (ELMA). K‐ras mutation was recognized in 85% (57/67) of SCs and 73% (11/15) of DCs, and multiple K‐ras mutations in 12% (8/67) of SCs and in 20% (3/15) of DCs. Multiple K‐ras mutations were also recognized in MCHs in 47% (14/30) of SCs and in 42% (5/12) of DCs. Moreover, the same sequence at K‐ras codon 12 in MCH and carcinoma was identified in 76% (32/42) of carcinoma cases and it was more frequently recognized in hyperplasias with histological atypia (51%, 37 of 72 foci) than those without atypia (24%, 16 of 68 foci) (P < 0.0007). These results further support the idea of multicentric carcinogenesis and premalignant potential of atypical hyperplasia in the human pancreas, although about half of the hyperplasias around carcinomas were not thought to be direct precursors.