I had an MRI that showed something the radiologist said could be this (painful) or that (soon-to-be lethal). He was reading the raw data, not giving an opinion. Doctor got all concerned and called him to get more specifics before talking to me. Turns out he was stating the possibilities, not likelihoods. After they had their talk, probably in jargon-y language and with maybe some medical history thrown in, doctor called me to give me the results interpretation, and at the time said he freaked out at the wording but got it straightened out. Although I'd seen the same results I decided I'd let the doctor tell me, even before I knew he was calling the radiologist. My gut feeling was it was a possibility, not a likelihood, because the painful thing was at a lot higher probability than the soon-to-be lethal thing. And it wasn't even "very rare."(1)
Yeah, your doctor felt she had to act NOW because if the test was accurate you probably would need to be drained right off. Don't know why it's that hard to get a phlebotomist. Here they're everywhere, willing and waiting to drain you. Not sure how an ER would be a shorter wait. Maybe you'll want to learn how to do your draining.
I try to be reassuring in my own weird way.
(1) I wonder if the machine showed many people suddenly with a very rare cancer in your area.