The 34-year-old was last seen about 10.45am on Monday 12 June 2017 at Trafford General Hospital.
He is described as a white, 6ft 1ins tall, of slim build, short brown hair, brown eyes and speaks with a Northern accent.
Mark was last known to be wearing a black tracksuit top with red piping down both arms, a black t-shirt and black jogging bottoms.
Sergeant Marc Foster, from GMP’s Trafford borough, said: “We are doing everything we can to find Mark and are appealing to anyone who might have seen him in the area.
“He is not in any trouble and we just want to make sure he is safe and well.
“Anybody who recognises Mark, or has any information about his whereabouts, should call police on 101.”