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.