There's never going to be a happy way to break bad news. But, as a recent column in the New York Times points out, physicians' efforts to perfectly stage their delivery may actually backfire and make things worse.
I can vouch for this. When I saw my primary care physician for an undiagnosed problem last year, she had a couple of my labs back, but a few more were still on the way. Without all the labs, she wouldn't speculate about a diagnosis. When she called a few days later with a diagnosis, she thought she was breaking bad news, but I was actually relieved because the silent, worried look with which she scruntinized the labs had convinced me that I was probably terminally ill.
So, to sum up, don't underestimate your patients' ability to read your poker face...or their hypochondria.