Inverted ductal papilloma of the lower lip: A diminutive lesion with no surface mucosal change

Inverted ductal papilloma (IDP) is a unique form of ductal papilloma that most often involves the lower lip and buccal mucosa. It is thought to arise from the excretory duct system at the interface of the submucosal minor salivary gland and the surface squamous epithelium. As such, IDP typically presents as a small well-defined submucosal mass with a ductal opening to the surface mucosa that varies in size and is clinically evident as a punctum or dilated pore. This feature is unique and may aid in narrowing the differential diagnosis. The present case report describes the clinical features, ultrasonographic images and immunohistochemical characteristics of IDP that appeared within the lower lip submucosa of a 37-year-old woman. As the present minute IDP was in the incipient phase of development, it was purely intraductal with a completely closed surface.