An unusual alimentary duplication cyst at the floor of the mouth--a proposal of new criteria for alimentary duplications.

In a 11-month-old boy, a cyst lined with non-keratinising stratified squamous epithelium and surrounded by striated muscle bundles with respiratory elements was found at the floor of the mouth. The cyst was excised without complications. As the cyst wall resembles the structure of the upper oesophagus, we think that this may be an alimentary duplication cyst, although it does not satisfy Lister's proposed criteria for alimentary duplications. To our knowledge, intraoral duplication cysts similar to the upper oesophageal tissue have not been reported previously. From the experience of this case, we propose new criteria for alimentary duplications.