Unsure of how far to push my doctor for reassurance

Hey @Nadi, so sorry to hear about yr new diagnosis. I would definitely seek a second opinion for your own peace of mind, either another gastric specialist or your oncologist for a review of your scans. 
Two of my children have special needs, one of them with a rare condition and I have learnt the hard way that doctors aren’t infallible and now I question absolutely everything and if I don’t feel a specialist is listening to me or understanding where I am coming from, I change doctors.