Metaplasia in the gut 1999; Vol. 32, N~ 3

14. Bahia 55, McMahon RE, Hobbisa J et al. Pelvic ileo-anal reservoirs: A lectin with dysplasia harbor additional mutations, such as those of the histochemical study Hiatochemical J 1993; 25: 392-400. p53 gene or the p16 gene and only these can be regarded as true 15. Campbell AP, Merreft MN, Kettlewell M et al. Expression ofcolonic antigens by tumor precursors. Compared with other organs, the role of meta- goblet and columnar epithelial cells in ileal pouch mucosa: Their association plasia and hyperplasia of the ductal epithelium in the tumorigene- with inflammatory changes and faecal stasis. J Olin Pathol 1994; 47: 834-838. sis of pancreatic cancer has not yet been defined and a sequence 16. Warren BE, Shepherd NA. Pouch pathology In: Nicholls RJ, Bartolo DCC, of stepwise mutations has yet to be discovered. Mortensen NJMcC (Eds.). Restorative Proctocolectomy. Blackwell Scientific Publications Ltd., Oxford 1993; 147-162. 17. Wright NA, Pike C, Elia S. Induction of a novel epidermalgrowth factor-secret- General remarks ing cell lineage by mucosal ulceration in human gastrointestinal stem cells. More than 90% of metaplastic and hyperplastic changes occur IR Nature 1990; 343: 82-85. the ductal system. For acinar cells, only focal acinar transformation 18. Sandborn W. Pouchitis following ileal pouch-anal anastomosis: Definition, has been described. This has also been termed acinar adenoma- pathogenesis, and treatment. Gastroenterology 1994;107: 1856-1860. 19. Kmiot WA, Williams MR, Keighley MRB. Pouchitis following colectomy and tous hyperplasia or acinar cell dysplasia, although this alteration is ilealreservoir construction for familial adenomatouspolyposis. Br J Surg 1990; not related to any neoplastic changes of the pancreas and has 77: 1283. been reported in various frequencies (1). The duct epithelium is 20. Merreft MN, Mortensen N, Kettlewell M et al. Smoking may prevent pouchitis assumed to be the site of origin of ductal pancreatic adenocarcino- in patients with restorative proctocolectomy for ulcerative colitis. Gut 1996; 38: mas. Therefore, interest has focused on epithelial changes that 362-364. might represent tumor precursor lesions. According to the World 21. Lohmuller JL, Pemberfon JH, Dozois RR et al. The relationship between pou- chitis after pouch-anal anastomosis and extra-intestinal manifestations of Health Organization (WHO) (2), four major types are distinguished: chronic ulcerative colitis. Ann Surg 1990; 211: 622-629. mucinous cell hypertrophy, papillary cell hyperplasia, adenomatoid 22. Penna C, Dozois RR, Tremaine Wet al. Pouchitis after ilealpouch-anal anas- hyperplasia and squamous metaplasia. Only the latter lesion is of tomosis for ulcerative colitis occurs with increased frequency in patients with nonmucinous cell type, and is preferentially observed in associa- associated primany sclerosing cholangitis. Gut 1996; 38: 234-239. tion with mechanical disturbances of the duct system due to pro- 23. King OW, Lubowski DZ, Cook TA. Anal canal mucosa in restorative procto- longed stenting (2, 3) or with certain types of chemotherapy (4). It colectomy for ulcerative colitis. Br J Surg 1989; 76: 970-972. 24. Ziv Y, Eazio VW, Sirimarco MT et al. Incidence, risk factors and treatment of does not appear to be related to the development of pancreatic car- dysplasia in the anal transitional zone after ileal pouch-anal anastomosis. Dis cinomas. All of the other lesions are of mucinous cell type. Interest Colon Rectum 1994; 37: 1281-1285. has focused on these lesions and studies have been undertaken to 25. Sequens R. Cancer in the anal canal (transitional zone) after restorative proc- determine their distribution in the organ and possible genetic muta- tocolectomy with stapled ileal pouch-anal anastomosis. Int J Colorectal Dis tions, such as the K-ras or p53 mutations, which are the most com- 1997; 12: 254-255. mon mutations in manifest carcinoma. 26. Shepherd NA. Pouchitis and neoplasia in the pelvic ileal reservoir. Gastroenterology 1995; 109: 1381-1383. 27. Gullberg K, Stahlberg 0, Liljeqvist L et al. Neoplastic transformation of the Duct lesions in normal pancreatic tissue pelvic pouchmucosa in patients with ulcerative colitis. Gastroenterology 1997; The distribution and frequencies of the different duct lesions in the 112: 1487-1492. normal pancreas could give a clue as to which lesions and sites are 28. Helander KG, Ahren C, Philipson BM et el. Structure of mucosa in continent high-risk for the development of carcinomas. The large studies by ileal reservoirs 15 to 19 years after construction. Hum Pathol 1990; 21:1235- 1238. Sommers (5), Cubilla and Fitzgerald (6), Kozuka etal. (7), Mukada and Yamada (8) and Kk~ppel et al. (9) have indicated that meta- plastic and hyperplastic duct changes occur most frequently in the jll~: ~r head of the pancreas, the preferential site of carcinomas. However, in these investigations often only one histological slide was evalu- Metaplasia in the pancreas ated per organ; hence the conclusions must be interpreted with caution. Systematic investigations of sections from the head, cor- J. Luttges pus and tail by Stamm (10) and by our group (submitted for publi- cation) have revealed that duct changes are evenly distributed Dept. of Pathology, University of Kiel, Germany. throughout the entire pancreas and do not share the same distrib- ution as carcinomas. Nevertheless, they increase beyond the age of 40 (5-7). They can even harbor a K-ras mutation at codon 12, as MetaplastiC and hyperplastiC Changes of pancreatic epithelium Tada etal. (11) and our group have shown. Lesions that harbor the K-ras mutation do not, however, preferentially occur in the head of affect almost exclusively cells of the duct system. The major types of such changes are squamous metaplasia, mucinous cell hyper- the pancreas. Therefore, other mutational events involving in par- ticular the lesions in the head region seem to be necessary for trophy (including pyloric gland and goblet cell metaplasia), ductal tumor progression. papillary hyperplasia and adenomatoid hyperplasia. They occur in normal, disease-free pancreatic parenchyma as well as in associ- Duct lesions in the tumor-associated pancreas ation with carcinomas and chronic pancreatitis. All types, preferen- tially those of the mucinous cell type, harbor K-ras mutations at In many organs, precursor lesions have been identified in the vicin- codon 12, the rate varying from about 6% in the normal pancreas ity of the established tumor and they provide information on the to 50% in tumor-associated tissue. However, since there is evi- development of the carcinomas. For the pancreas, several studies dence that these lesions are evenly distributed in the normal pan- on carcinomas (6, 7, 9) have indicated that mucinous cell hyper- creas and since they do not show a preponderance in the head trophy is the most frequent type of lesion in these organs, followed region, the preferential site of ductal adenocarcinomas, their role by papillary hyperplasia, adenomatoid hyperplasia and squamous as a tumor precursor should perhaps be reconsidered. Only lesions metaplasia. Molecular analyses have revealed high frequencies of

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the K-ras mutation especially in the mucinous cell type (12), 11. Tada M, Ohashi M, Shiratori Y at al. Analysis ofK-ras gene mutation in hyper- although no spatial relationship between the carcinomas and K-ras plastic duct cells ofthe pancreas without pancreatic disease. Gastroenterology mutation positive lesions could be established (3). Of special inter- 1996; 110: 227-231. est are duct lesions that show dysplastic changes, as they appear 12. Mataubaysahi H, Watanabe H, Nishikura K at al. Determination ofpancreatic ductal carcinoma histogenesis by analysis of mucous quality and K-ras muta- to be the most likely tumor precursors. Molecular approaches have tion. Cancer 1998; 82: 651 -660. revealed that they harbor K-ras mutations at codon 12 in a range 13. Moskaluk CA, Hruban RH, Kern SE. p16 andK-ras gene mutations in the intra- trom 55-75% (12, 13). In addition, Moskaluk eta!. detected muta- ductal precursors of human pancreatic adenocarcinoma. Cancer Res 1997; tions of the p16 (MTS1) gene, which is also frequently found in 57: 2140-2143. manifest carcinomas (13). A model of tumor progression compara- 14. Brat DJ, Lillemoe KO, Yeo CJ at al. Progression ofpancreatic intraductalneo- ble to that for colorectal cancer has been suggested by Brat et al. plasias to infiltrating adenocarcinoma of the pancreas. Am J Surg Pathol 1998; 22:163-169. (14) with emphasis on the degree of cellular atypia. However, it has 15. Becker V. Carcinoma ofthe pancreas and chronicpancreatitis - apossible rela- been pointed out that it is especially difficult to distinguish papillary tionship. Acts Hepatogastroentarol 1978; 25: 257-259. ductal hyperplasia with severe dysplasia from intraductal exten- 16. Cylwik B, Nowak HF, Puchalaki Z at al. Chronische Pankreatitis ats sions of the primary carcinoma. prddisponierender Faktor in der Entwicklung des Pankreaskrebses. Zentralbl AlIg Pathol Pathol Anat 1985; 130: 217-224. Lesions associated with chronic pancreatitis 17. Lowentels AR, Maisonneuve P, Cavallini G at al. and the International Pancreatitis Study Group. Pancreatitis and the risk of pancreatic cancer. N Chronic pancreatitis is considered a risk factor for the development EngI J Med 1993; 328: 1433-i 437. of pancreatic ductal adenocarcinoma (15-18). So far, two histolog- 18. Sgambati SA, Lawton GP, Modlin IM. Chronic pancreatitis: A precursor to pan- ical studies have searched for possible precursor lesions in this dis- creatic carcinoma? Dig Surg 1994; Il: 275-285. ease (9, 19). It was found that nonpapillary epithelial hypertrophy 19. Volkholz H, Stolte M, Becker V. Epithetial dysplasias in chronic pancreatitis. Virchows Arch [A] Pathol Anat 1982; 396: 331-349. (mucous cell type) was the most frequent (68%), followed by pap- 20. Cylwik B, Nomak HF, Puchaiski Z at al. Epithelial anomalies in chronic pancre- illary hyperplasia and squamous metaplasia (both 11%). Severe atitis as a risk factor of pancreatic cancer. Hapatogastroenterology 1998; 45: dysplasia or ductal carcinoma in situ lesions were not observed. In 528-532. contrast, in a study of 70 resection specimens from patients with 21. Tabata T, Fuilmoro T, Maeda Set al. The rote ofras mutation inpancreatic can- chronic pancreatitis, severe dysplasia was reported in 8.6% of the cer, precancerous lesions, and chronicpancreatitis. lot J Pancreatol 1993; 14: cases and advanced fibrosis associated with dysplasia in 65% 237-244. 22. Muller J, Gansauga 5, Schmid R at at. p53 aber nicht K-ras Mutationen kon- (20). The authors even concluded that surgical removal of these nan in der chronischen Pankreatilis gefunden warden (p53 butnot K-ras muta- lesions should be recommended. Tabata eta!. (21) and MOller eta!. tions are found in chronic pancraatitis). Langenbacks Arch Chir I (Forumband (22) also reported severe dysplasia in chronic pancreatitis, 1997) 1997; 715-718. although this is not convincingly demonstrated by their illustrations. Because of the clinical importance and the major consequences for the patients, a general and reproducible definition and classifica- jg ~ ~ ~ -. ~ 4~4 4=iiL>A~ tion of the degree of cellular atypia and dysplasia are needed. An example of this is provided by the WHO classification (2). Functional aspects Moreover, such duct lesions need to be better characterized so that true high-risk lesions can be evaluated. of gastrointestinal metaplasias

References N.A. Wright 1. Solcia E, Capella C, Klbppel C. Tumors of the pancreas. In: AFIP Atlas of Tumor Pathology. 3rd series, fascicla 20. Armed Forces Institute of Pathology, Imperial College School ot Medicine, Hammersmifh Hospital, Washington, DC 1997. Imperial Cancer Research Fund Histopathology Unit, London, UK. 2. Klbppel G, Solcia B, Longnecker OS et al. Histological typing of tumours of the exocrine pancreas. In: WHO International Histological Classification of Tumours. 2nd ad. Springer, Berlin 1996. There are several different types of metaplasia in the gastrointesti- 3. Lijttges J, Schiehe B, Menke MAOH at al. The K-ras mutation pattern in pan- nal mucosa. In the stomach, the most widely recognized of the sev- creatic ductal adenocarcinoma is usually identical to that in associated normat, eral different types is, of course, intestinal metaplasia, which occurs hyperplastic and metaplastic duct epithelium. Cancer 1999; 85: 1703-1710. 4. Washington K, Peters W, Gotttried MR. Pathology of the pancreas in bone in atrophic gastritis and Barrett’s esophagus. In the main, but with marrow transplant patients. Hum Pathol 1993; 24: 152-159. significant differences, this mucosa replicates the functional profile 5. Sommers SC, Murphy SA, Warren S. Pancreatic duct hyperplasia and cancer of intestinal epithelium. However, there are other metaplasias that Gastroenterology 1954; 27: 629-840. appear to have a secretory profile that distinguishes them. Two of 6. Cubilla AL, Fitzgerald PJ. Morphological lesions associatedwith human primany them will be discussed: the so-called ulcer-associated cell lineage invasive nonendocrine pancreas cancer Cancer Has 1976; 36: 2690-2698. (UACL) in the intestinal mucosa and pseudopyloric metaplasia in 7. Kozuka 5, Sassa H, Taki Tat al. Relation ofpancreatic duct hyperplasia to car- the gastric mucosa. cinoma. Cancer 1979; 43: 1418-1428. 8. Mukada T, Yamada S. Dysplasia and carcinoma in situ of the exocrine pan- creas. Tohoku J Exp Mad 1982; 137: 115-124. The ulcer-associated cell lineage 9. Klbppel G, Bommer G, RuckertK at al. Intraductalproliferation in the pancreas For many years now, pathologists have remarked on the emer- and its relationship to human and experimental carcinogenesis. Virchows Arch gence, in chronic intestinal ulcers in the human gut, of tubular [A] Pathol Anat 1980; 387: 221 -233. structures containing mucin-producing Cells that are quite dissimi- 10. Stamm BH. Incidence and diagnostic significance ofminor pathologic changes in the adult pancreas at autopsy: A systematic study of 112 autopsies in lar from those of the indigenous cell lineage (1-4). These complex patients without known pancreatic disease. Hum Pathol 1964; 15: 677-683. structures are confined to the lamina propria, usually close to the

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