Ok so for a diagnosis stated specifically as neuroendocrine carcinoma of pancreas will definitely fall under the C7A- category. Best way to explain this is just by your ICD-10-CM index, if you go to Carcinoma>Neuroendocrine, it guides you to this specific section of codes.
Now, C7A.094 of the foregut also is a good option for the specific diagnosis above since the foregut does include the pancreas.
There are 3 distinct sections; foregut, midgut and hindgut.
Foregut gives rise to the esophagus, stomach, liver, gallbladder, bile ducts,
pancreas and proximal duodenum. The midgut develops into the distal duodenum, jejunum, ileum, cecum, appendix, ascending colon, and proximal 2/3 of transverse colon. The hindgut becomes the distal 1/3 of the transverse colon, descending colon, sigmoid colon and the upper anal canal.
Also, here is an interesting article in regards the physiology of NETs (Neuroendocrine tumors)
hope this helps!