There are two types of epithelial metaplasia of the pancreatic duct: mucous cell metaplasia and squamous cell metaplasia. The former is often involved in papillary protrusion compatible with mucous cell hyperplasia, which occurs at multiple sites and shows age-related increases in frequency, approaching 100% in the elderly. Mucous cell metaplasia/ hyperplasia is usually associated with naked islets of Langerhans and branch duct remnants due to parenchymal/acinar loss. Cystic dilatation of the branch pancreatic ducts in postmortem pancreatography is also increased with age-related frequency. The epithelia of the cystic dilated duct are composed of mucous cell metaplasia/hyperplasia. Therefore, age-related pathological conditions of the pancreas consist of mucous cell metaplasia/hyperpla-sia, cystic dilatation of the branch ducts and naked islets of Langerhans, which occur in this order. Some hyperplasias show similar clinical pictures to intraductal papillary-mucinous tumor (IPMT), leading to a series of, or relevant to, both ductal lesions.

Copyright © 2007 S. Karger AG, Basel

According to the description of the intraductal papillary-mucinous tumor (IPMT)/intraductal papillary-mucinous neoplasm (IPMN) by the AFIP (Armed Forces Institute of Pathology), 'this is an intraductal pancreatic tumor formed of papillary proliferations of mucin-producing epithelial cells that have some gastroenteric differentiation [1].' Mucinous cystic tumors (MCTs)/mucinous cystic neoplasms (MCNs), however, are cystic pancreatic tumors formed of epithelial cells producing mucin; there is evidence of gastroenteropancreatic differentiation and an 'ovarian-type stroma [1].'

Fig. 1. Mucous cell metaplasia/hyperplasia. Tall columnar/mucinous epithelia arranged in mildly dilated and papillary proliferation in the lumen of the branch pancreatic duct. HE. X100.

In the pancreas, especially in the elderly, IPMT-like non-tumorous epithelial changes occur [2]. Kimura et al. [3] reported that small non-neoplastic cystic lesions were found in nearly half of the 300 patients studied and the prevalence increased with age.

In this chapter, age-related lesions/findings of the pancreas are described and compared between IPMTs and MCTs.

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