My friend just texted me her father has cancer. I'm so afraid I'll say something inappropriate

How do I comfort her? Anything that'll help her? I don't want to say something tone deaf because there's no way I'll ever truly understand how it's like to have your parent being diagnosed with cancer. I feel so bad that I don't even know what to say to her. She's a strong woman, and she's kind, I have no idea why she and her father and her family has to go through this. Please tell me something that could make her feel even just a little bit better.