Lesbien and muslim howe to tell parents?

hi i am a 25 year old women and muslim i am lesbien. I wonder if anyone have a idea howe to tell your parents. My parents are pretty open minded but i think this will be a big shock for them so i don't know if i should tell or not. And howe is the best way to explain it. I know many think of this as as a sin but howe can it be it is nothinging i have choosen myself.