After learning she has a brain tumor, Amelia calls in her old neurology professor (guest star Greg Germann) to help her figure out how to treat it. 'He's the most arrogant teacher I ever had,' Amelia tells DeLuca, before Dr. Tom Koracick makes her admit he's 'the best.' Watch this sneak peek from Season 14, Episode 3, 'Go Big or Go Home' and don't miss Grey's Anatomy THURSDAYS 8|7c on ABC.