Immediately, and I mean immediately refer her to a hospital (search a good hospital around your area). Don't come to conclusion that it is cancer, think positive. Do lots of dua!! I know you're scared, I've gone through this, this time last year, however my dear mother (Allah yar7ama) passed away early January because the cancer had spread throughout her neighbouring organs but it was too late... they said it was kidney stones but then we went to Saudi in summer 2010 to do Umrah during Ramadan, and the doctors there said it was actually cancer, then we went to a good hospital (where we live - London) and they confirmed it. It was the hardest time of my life, I know it's one of the greatest test I've ever had and probably will ever have, I've unfortunately experienced the passing away of my mother at a young age of 15. Now I'm 16, but thankfully Allah helped me through this and my siblings were with me. And there's a reason to everything. I still miss her so so so much, but this was Allah's plan that I can't change however through this tough period of my life, I've become so much closer to Allah than I ever was... May Allah grant her the highest Jannah inshAllah.
So I beg you to send your mother straight away to the hospital for a check up. I sincerely hope she's okay. Again, stay positive and do dua. What's written is writen but don't lose hope in Allah.
Tell your mother, she should go to the hospital for a checkup (say 'just in case') but don't tell her what you suspect it is, don't even mention you searched through the symptoms. Just tell her to go. I know it's hard but stay strong.
I wish you and your mother the best. I'll definitely do dua for your mother!! Take care...