Hello, My Mom Had A Lump On Her Arm, That

Hello, my Mom had a lump on her arm, that her doctor removed and sent for a biopsy. The Doctor called her and said that the results of the lump came back showing cancer. It was about a 3-4cm bump that started off small (she thought it was a pimple) and didn't grow for about two years and then started growing in December. Is she going to die? I am so scared and can't stop thinking about it.