The cause of primary umbilical endometriosis is unknown; however, one theory is that endo-like cells implant near the scar tissue that creates the belly button. Another is that cells left over ...

Your belly button is a scar, your very first one. It forms when a doctor snips your umbilical cord, and, depending on how it heals, you could have an outie or, more likely, an innie. And innies ...