So sorry, :hugs does look like it could be cancer. :idunno Is she suffering? If not, you don't need to euthanize her, but I will support you decision either way. :hugs
If you do euthanize, can you cut one of the pumps open and take pictures of it?
All of the maggots need to come off ASAP. I think most people suggest flushing with saline and picking them off by hand. It's truly one of the most disgusting things I have done, but trust me when I say all maggots must come off today.