A girl of nine who went to hospital in Greece suffering from abdominal pains was found to be carrying her embryonic twin.
Andreas Markou, head of the paediatric department at Larissa hospital, said that doctors examining the girl found she had a growth.
They operated to remove what they believed to be a tumour. But a biopsy showed it was a six-centimetre long embryo with hair, eyes and a spine but no brain.
The hospital said the girl’s family does not want to be identified. They said the girl was doing well after the surgery.
Cases where one of a set of twins absorbs the other in the womb occur in one in every 500,000 live births.