Cleveland State took permanent control with a 12-0 run in which Illinois-Chicago went scoreless for 5:53. Lee's 3-pointer ignited the surge, and Devon Long added five points.
Long's three-point play with 13:58 remaining gave the Vikings a 46-28 lead, and the Flames got no closer than seven points the rest of the way.
Mason was 8 of 12 from the field and added six rebounds. Lee finished with 10 assists.
Colorado State graduate transfer John Gillon has chosen Syracuse, giving the Orange a potential starter at point guard entering the 2016-17 season.
DeSean Murray, who averaged 20.2 points as a sophomore at Presbyterian, will transfer to Auburn to play for coach Bruce Pearl.
Former Kentucky guard Ed Davender, the only Wildcat with at least 1,500 points and 400 assists, has died. He was 49.