Dr. Paul Grabb, a pediatric nerosurgeon, said he was surprised when he discovered a small foot growing inside the brain of 3-day-old Sam Esquibel.It was thought to be a teratoma — a congenital brain tumor composed of foreign tissue such as muscle, hair or teeth — or a fetus in fetu, which is a developmental abnormality in which a fetal twin begins to form within the other.Teratomas are already a rare congenital brain tumor, but to be found in this complex of a form (foot) had never been heard of. The foot was found and surgically removed in 2008. Everything was a success and went on being treated like it was any other teratoma.