Tim said it very well, your mother's diagnosis, surgery and clean cystos would not lead one to think that aches and pains are due to metastases. How could you know.
I think it's great that you took some time off to be with your family. It's a very hard time. Make sure you take care of yourself as well, as cancer is hell on caregivers. I didn't follow that advice while caring for my sister during her fight with breast cancer, to my own detriment, the stress can be overwhelming.
All the best to you, you sound like a wonderful son.
Wendy