A new aspect of gastric metaplasia in Crohn's disease: bidirectional (foveolar and pyloric) differentiation in so-called 'pyloric metaplasia' in the ileum.

Mucus-secreting cells found at the site of ileac ulceration in Crohn's disease have been described as 'pyloric metaplasia'. Using mucin-histochemical methods and immunohistochemical stainings for Ki-67 antigen and foveolar-type mucin (M1) of the stomach, the characteristics of this type of metaplasia were studied in surgically resected ileac specimens from two Japanese patients with Crohn's disease. Not only pyloric-type cells but also foveolar-type cells were demonstrated; often displaying an organoid growth of the normal stomach mucosa. Stem cells of the ileac crypt may differentiate potentially to intestinal-, pyloric- and also to foveolar-type cells. The term 'pyloric metaplasia' is not appropriate and 'gastric metaplasia' should be used when describing this type of metaplasia.