I think in a lot of instances 'miraculous' healing of cancer is shorthand for, "oops, we read the CAT scan / MRI wrong." If there's a tumor there and the doctor doesn't catch it, he/she will probably get sued down the road when the patient is finally diagnosed. This gives them an incentive to err on the side of diagnosing an illness, even if it isn't there. If later test show that there never was a tumor, they can't very well just come out and admit they screwed up - again, this gets them sued for being incompetent and causing mental distress. So when this happens, the doctor will likely give some line like, "Wow, I've never seen anything like this. That tumor just disappeared. Someone upstairs must be looking out for you." The patient probably prayed, or had someone in their family pray for them, so they go away feeling like a special snowflake because god miraculously healed them. The doctor doesn't get sued, so everyone is happy with the exception of atheists who have to listen to yet another "miracle healing" story.