Daniel Munoz added 12 points and John Schoof 11 for American (8-14, 3-4), which shot 52.3 percent (23 of 44) from the floor. Lumpkins was 8 of 10 from the field and combined with Munoz to make all 16 of the Eagles’ free throws.
Schoof’s 3-pointer with 6:47 left in the first half broke a 14-all tie and sparked a 15-2 run for American. Lumpkins capped the run with a three-point play.
Seth Hinrichs led Lafayette with 18 points and Bryce Scott went 5 of 5 from 3-point range for 17 points, but the Leopards (11-13, 4-3) could not overcome a 26.1 percent (6 of 23) first-half shooting performance.
American, which snapped a two-game skid, held a 31-22 rebounding advantage and dished out 14 assists to six turnovers.