A girl's twin was inside her stomach

Sounds interesting? I found this news on the net. Well, here is the story. A 9-year-old girl in Athens, Greece, went to hospital suffering from stomach pain was discovered to be carrying her developing twin. Doctors checked up the girl and surgically removed a growth that they later revealed as an embryo about two inches long. They saw on the right side that her stomach was swollen. They couldn't think that this lump would hide an embryo. This sounds strange. Well, that could possibly happen. They said that the embryo was a shaped fetus with a head, hair and eyes, but no brain nor umbilical cord. This is a very rare case. What do you think about this?