Metaplastic bone formation in a hyperplastic polyp of the stomach: a case report.

Metaplastic bony tissue along with hyperplastic mucosal epithelium showing no atypism was detected in biopsy materials from a Yamada type I gastric polyp. The tissue was metaplastic woven bone associated with calcification. Histogenesis of the bone formation is as yet unknown. This is the first reported case of the presence of metaplastic bone accompanied by hyperplastic gastric mucosa so far.