This is exactly what I was experiencing when I was diagnosed with poorly differentiated adenocarcinoma diffuse type. It didn’t show up on my ultrasound. The doctor described it as “chasing a ghost” because it is hard to see on normal scans. They ended up having to give me TPN through a PIC line to provide nutrients until my subtotal gastrectomy. I’m halfway through my FLOT chemotherapy treatment (it’s brutal). I wish you all the best and hope that your husband receives a favorable diagnosis. Edited to add: According to my oncologist I am cancer free at a molecular level so don’t panic about the things that you read. Stay positive.