However, last year, eight years after the stem cell operation, the woman, then 28, complained of increasing pain in the area.

Doctors discovered a three-centimetre-long growth, which was found to be mainly nasal tissue, as well as bits of bone and nerve branches that had not connected with the spinal nerves.

Neurosurgeon, Brian Dlouhy from the University of Iowa Hospitals and Clinics in Iowa City, who removed the growth, said it was benign, but was secreting a ‘thick copious mucus-like material’, which was probably why it was painfully on her spine.