Hello Jeff, I'm sorry for your mother.
However, I can reassure you that it has not been the microwave to cause cancer. They self-contain radiation because of the way they are designed: the panel on the door with all the small holes in it has the purpose of shielding the exterior from microwaves (as well as the inner plating on the walls). There is quite a lot of physics behind how this work (let's say 6 months of Uni), but the moral of the story is: don't worry about your health if you use it. If you want to be expecially cautious, avoid being in super close proximity of the microwave (10 inches or 30 cm) for prolonged periods of time, but it is probably already not necessary.
Wish you all the best!
