You know, if we're willing to accept Anime filler, then the Mizuki returns arc is strong evidence for some kind of Tiger Sage Mode.

In that arc, Mizuki is given a curse mark by Orochimaru but rather than transform him directly it gives him instructions for a medicine that gives him similar powers to the course mark. The initial form bulks him up and gives him tiger-stripe markings. Stage two turns him into an anthro-tiger.