The score was tied at 36 at the half before the Lions (14-14) shot 66 percent from the field and outscored the Tigers 50-28 over the final 20 minutes.
Darius Smith added 14 points, Adrian Caldwell had 12 and Allen Young 10 for Paine, which will play Benedict (21-6) at 7:45 tonight in the semifinals.
Stephenson and Kedric Taylor had nine rebounds each.
Stillman's Jeffrey Wherry scored a game-high 22 points but was only 4 of 14 from 3-point range. As a team, the Tigers were 6 of 36 from beyond the arc.
In the women's tournament, Sharnita Lloyd scored 24 points to lead Kentucky State to a 73-70 victory over Paine.
Jasmine Davis added 13 and Style Harper had 12 for the Thorobrettes (15-11).
Paine’s Ashley Watts led all scorers with 29 points. Lashonda Canty added 14 points and grabbed a game-high 12 rebounds. Watts had nine rebounds for the Lady Lions (12-16).
Kentucky State led 30-24 at the break before Paine opened the second half on a 13-3 run and took a 37-33 lead on a three-point play by Kiara Johnson with 16:53 to play.
The Thorobrettes took the lead for good at 43-41 on two free throws by Shayla Moore with 11:54 remaining.