Unfortunately, Duncan was euthanized this afternoon as the vet deemed the cancerous tumor inoperable.  The tumor had invaded so much of Duncan's face/eye that there just wasn't anything he could do. When the vet first saw Duncan in person, he took a step back and said "Oh Gail, we can't fix this at all."  
I guess I was in shock or something because I asked him "Why Not"?  Our vet has always been willing to go the extra mile on procedures to help horses.  He has done surgeries, skin grafts, hair transplants, massive wound care, etc.  I suppose I thought he would be able to wave his magic "Vet Wand" and make Duncan whole again.
He showed Kristy and I the large blood vessels that had developed along Duncan's jaw that had become prominent due to the demand for blood by the tumor.  The tumor had destroyed his eye and there was no telling how much invasion there had been. 
Our vet, his assistant, myself and Kristy were devastated.  This situation was absolutely senseless.  Duncan was only about 10 years old!!!  He was kind, well mannered, almost 16 hands tall and beautiful. If he had been treated when the tumor first appeared this story most likely would have had a much different ending.  The Vet estimated that this had been going on for over a year untreated.
Farewell Dear Duncan.  Know that many of us cared and wanted so much more for you.