At the age of 18, a teenager has finally had his 17cm tail removed by surgeons after hiding the defect all his life.
The young man, from Nagpur, India, went to hospital complaining the growth had become painful.
Doctors explained it was a vestigial tail that developed while he was in the womb - but should have disappeared naturally over time.
A neuro-development abnormality had meant it continued to grow while his spine was forming - despite the body usually absorbing the tail to form the back.
"He was admitted only after he complained of extreme pain in his lower back, problems while sleeping and sitting.
"The boy was also suffering from an extreme psychological issue because the tail was growing so he had to always adjust the tail in his clothes when sitting."
He added: "The family were always aware but they ignored it and did not see a doctor as they were superstitious and considered it to be a good luck charm for the boy.
"They hid his condition all these years worrying about the social stigma and also because it was not creating any health issue for him until now.
"He is very happy. He is now very comfortable while sleeping and sitting. He says he feels more confident about himself now."
After six weeks of pregnancy, every growing baby possesses a vestigial tail - but it normally disappears during development as it grows to become the spine and nervous system.
However, sometimes children are born with one as a result of it continuing to grow - but there have only been 23 cases reported worldwide.
They contain adipose and connective tissue, blood vessels, nerves and are covered by skin.
Doctors say they are harmless and can be easily removed because they lack bone and cartilage.
But the abnormality can affect the bladder and reduce bowel control. It has also been known to result in extreme pain and a loss of function in the lower body.