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17 July 2012, 16:26
Detectives believe the assault happened sometime between 3.45am and 4am on Sunday 15 July.
He was attacked near the taxi rank at the junction of Spinning Jenny Way and St Helens Road in Leigh.
During the assault, a part of the man's right ear was bitten off and he has had to have reconstructive surgery.
Detective Constable Richard Willoughby said: "The area was quite busy around the time of this incident and I hope that someone in this crowd may have witnessed this assault.