Tumours can be malignant (cancerous) or benign (non-cancerous) so he may well have had an actual tumour. In addition to various blood tests, ultrasound, MRI, CT and an upper GI series the one guaranteed method of diagnosis is a biopsy. It'* possible there was tumour not determined to be benign until after a biopsy or surgery to remove the mass. I can't quote percentages off the top of my head but as memory serves malignancies are of a much greater proportion. This whole issue was also likely clouded by the blood work which, since the actual diagnosis was pancreatitis would certainly not have returned as normal. Imaging would also have shown an altered physical appearance due to the inflamation.

Often a diagnosis (in general terms) is made by a specific set of criteria. Some patients haven't "read the book" and present slightly different than what is expected. This can make the accuracy of a diagnosis subject to a larger margin of error.

you know thats all they can do, right? its kind of hard to tell for sure in most cases, until someones dead and you can dissect them. or you could try dissecting them before theyre dead, but im sure someone would complain.

when someone dies isnt exactly up to the doctors.

Yeah, I wasn't really serious. As much technology and testing as we have, there will always be 'trial and error.'

Ddalder, I researched right after I posted and did find out some complications in diagnosing based on certain tests. I tried to find some stats on how often it can be misdiagnosed, but didn't.

Being a doctor is just like being a human mechanic. You can do a few scans, you can see symptoms, check fluids, but you only really know what'* going on whats you rip into 'er