Scrambles are pass plays, by definition. The quarterback scrambles for positive yardage when he's under pressure or when all his receivers are covered. Sometimes he runs just because a big hole opens up in the pass rush and it's going to be easy to gain yardage. But every scramble begins as a pass play. Scrambles are essentially the positive version of sacks.
Scrambles are also run plays, by a different definition. They count as rushing yardage in the official NFL stats. They are listed in the play-by-play as running plays. Here at Football Outsiders, we've always counted scrambles as running plays because they are runs in the standard play-by-play.