Top case started to crack like glass

Hi, the topcase of my macbook started cracking, the cracks look almost as if it was made of glass. I do not know how this might happen without direct pressure on the laptop itself.. i do not use a watch nor any bracelets which i think would've made different damage (That's what people told me on different forums.. ).

I don't want my computer to simply disintegrate. What do i do? Can i get this replaced? I keep my laptop in a hard closed case at all times when not used. I've never put anything heavier than my hands onto it when it was opened. I'm already over my warranty.

The damage is on both sides of the palmrest. You cannot feel it.