It's not just women who have breasts, but breasts sometimes do increase in fullness during sexual arousal, and that is believed to be about blood flow. 25% sounds like the max you'd probably see in that to me, though, more than a norm.
I think it's safe to say it won't usually be that obvious or dramatic for most people, and no matter any increase, it's also temporary. If it happens, once someone isn't excited anymore, their breasts will look like they did before.
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