Board Thread:Naruto Discussions/@comment-4271790-20141016102132/@comment-26302001-20141017080148

btw, everyone check out chapter 673 page 13, Kishi uses Tobirama to hint at Sasuke gaining the Rinnegan because he was on the verge of death, after Kabuto injected his heart with Hashi DNA. Completely matches and lines up with Madara gaining Rinnegan, I think the only reason his is different is because he has six paths sage chakra when he awakened it, from the sage himself, so it got a slight upgrade(sharingan powers added to it, hence the tomoe)