Paneth cell adenoma of the ileum

A Paneth cell adenoma of the ileum was recently found in a 47-year-old male with familial adenomatous polyposis (FAP). The patient had years previously been subjected to a total proctocolectomy. Following surgery, endoscopical biopsies were obtained from the duodenum (10 biopsies) in four instances and from the ileal pouch (6 biopsies) in three. All biopsies were taken between 1988 and 2003. Hematoxylin and eosin (H&E) sections from all those 16 biopsies were reviewed. In one biopsy from the ileal pouch, a tubular adenoma carrying 92% dysplastic Paneth cells was found. Paneth cells were more easily singled out when H&E sections were observed in a fluorescent microscope than when using conventional transmitted light, or lysozyme immunostain. Despite a wide distribution of Paneth cells in mucosas with intestinal metaplasia (e.g. Barrett's esophagus and gastric intestinal metaplasia), in the normal small intestine and in the large intestine with chronic inflammatory diseases only a few Paneth cell neoplasias have been reported in the GI tract. The cause of the apparent natural resistance of these specialized cells provided with anti-microbial and growth factors to undergo neoplastic transformation deserve further investigation. A review of the literature indicates that this is the first reported case of Paneth cell adenoma of the small intestine.