This is an old joke but a recent experience with a surgeon taking out a long segment of bowel worried about a tumor without mentioning a site for the tumor or a solid reason why he thought there was a tumor reminded me of how true this can sometimes can be.

An internist, a surgeon and a pathologist decided that they were working too hard and that they should go duck hunting together.

A couple of mornings later found them sitting in a duck blind waiting for the birds. Pretty soon a bird appeared on the horizon.

The internist watched it carefully as it came over and said, "Gentlemen, observe the colorful plumage, the quacking call and the web feet trailing behind."

As the bird disappeared out of range, he said, "Based on my observation, I would venture that we have seen a duck, but further tests may be necessary before we decide on a course of action."

The surgeon was furious.  He told the internist, "It looked like a duck, it quacked like a duck, it was probably a duck."

The other doctors looked blankly at him, but there was a slight sneer from the surgeon.

It wasn't long until another bird appeared. They waited until it came closer and then the surgeon leaped to his feet with his gun. He started shooting wildy.

Feathers and pieces of feet, blood and guts and bill exploded overhead.

A sorry looking carcass fell to the ground.  

The surgeon turned to the pathologist and said "Go over there and tell me if that is a duck."