They found a tumor in my grandma

So I dont really know what group this belongs in, I'm really just looking for support right now. I'm 17 and just started my senior year of high school. This week started out greatly and is quickly declining. My grandma is my best friend and I tell her everything. Today they found a tumor on her liver and it scares me more than anything. Early in the summer when I came to the realization that there was a good chance my pap wouldn't be here to see me graduate, it hurt. But I knew if something actually happened and he wasn't here he would be watching over me. But now I have to face the fear of now neither of my grandparents might not be there. It sounds so awful to say but it's a real fear. I'm scared I passed up too many chances to hang out with my grandparents. I'm really just looking for some positive thoughts and advice.