A student at Indiana University was slowly being killed by her evil twin which was living in her brain.
When doctors first discovered the tumor they said it was too risky for surgery.
As it grew in her brain, Yamini Karanam, 26, began losing the ability to read, walk and eat.
Finally a neurosurgeon in California removed the tumor, which turned out to be a teratoma.
It contained bone, hair and teeth - what many experts say is a twin that never developed and was absorbed into her body.
She's now expected to make a full recovery.