I had the endoscopy today. I don't have the written report, but the Gastroenterologist told me afterwards that I have a stricture in my esophagus caused by something pressing on it. Probably the tumor. Normal diameter for an adult esophagus is 2-3 cm. At the stricture, the diameter of my esophagus is 1 cm. So at least we have an explanation for the problem. I think that they took some tissue samples to biopsy from the duodenum (the upper part of the intestine that a colonoscopy does not get), but I was still coming out from under the anesthesia, so my memory is somewhat fragmentary. The doctor also discovered that I have a thrush infection in my esophagus. No idea how long it has been lurking there. I am on an antifungal to try to eradicate it.
Most likely will have a stent put in to open up the esophageal stricture next week.