Congenital Midline Sinus of the Upper Lip

A case report of a congenital midline sinus of the upper lip in a 44-year-old white man is presented. The patient had a midline, pit-like opening superior to the vermilion border of the upper lip and extending to the anterior nasal spine. Microscopic examination revealed that the sinus consisted of keratinized stratified squamous epithelium with sebaceous glands. Six other cases have been reported in the world's literature and are reviewed. The varying embryological theories describing the formation of the upper lip are considered. It is concluded that the formation of this rare midline congenital anomaly is best explained by the mesodermal “merging” theory of facial embryonic development, rather than the classical theory of peninsular “fusion.”