Life is crazy weird
Doctors at Larissa General Hospital examined the girl and surgically removed a growth they later discovered was an embryo about six centimeters (more than two inches) long.
"They could see on the right side that her belly was swollen, but they couldn't suspect that this tumor would hide an embryo," hospital director Iakovos Brouskelis said.
The girl has made a full recovery, he said.
Andreas Markou, head of the hospital's pediatric department, said the embryo was a formed fetus with a head, hair and eyes, but no brain or umbilical cord.
Markou said cases where one of a set of twins absorbs the other in the womb occurs in one of 500,000 live births.
The girl's family did not want to be identified, hospital officials said.