[Omphalolith]

In rare instances a hard, smooth, almost black bolus, "omphalolith" is found in the umbilicus, resembling a malignant melanoma. After removal by a pincette it reveals on its backside a colourless lamellar epithelium. At microscopic examination it also constists of stratified corneocytes. Differential diagnosis of the omphalic stone includes the so called umbilical cholesteatoma, an accumulation of crumbling, fetid masses in the umbilicus, often times accompanied by seborrhea which may lead to abscess formation. The term omphalic stone could not be found in the medical literature. However, it has been used to name a jewel which is worn in the umbilicus or a huge stone in Delphi which was believed by our ancestors to be the center of the world.