A 9-year-old girl in Greece entered a hospital with stomach pains and left grieving a twin she never even knew existed. The girl, whose name has not been revealed, had a swollen belly and abdominal pains that doctors at Larissa General Hospital attributed to a tumor. After the growth was surgically removed, they discovered that it was actually the girl's embryonic twin.

"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 embryo was a formed fetus measuring more than two inches long. There was no brain or umbilical cord, but there was a head, hair and eyes.

While cases of one twin absorbing the other in the womb is unusual, it isn't completely unheard of. Andreas Markou, head of the hospital's pediatric department, says it happens in about one of every 500,000 live births.

The girl made a complete recovery, but not surprisingly, her family wishes to remain anonymous.