Definitely get a 2nd opinion & see a NETS surgical oncologist. Your symptoms are exactly like I had; vomiting, horrible diarrhea & abdominal pain that would double me over. I had a small bowel obstruction, mine was also in the mucosa/submucosal, 4 of 24 lymph nodes were removed. I had no further treatment (except for CT scans/bloodwork/PET scan) every 6 months until 2 years later & cancer had metastasized to liver, abdomen, peritoneal lining, gallbladder, diaphragm, appendix, that led to another painful surgery. Started Octreotide injections 3 wks after surgery. You have to be your own advocate based on how you feel & symptoms! I think Drs sometimes tend to lump patients together based on their experiences with other patients. Get a 2nd opinion & share what you find out. I wish you the best!