I had surgery Monday, and am home now, and many thanks for all of the kind thoughts and good wishes; apparently, there's something to be said for positive thinking, because
I got my wish - it was a big ass cyst (29 cm x 25.7 cm x 15.3 cm); don't know what the weight was, but between the time anesthesia started and ended, I lost 22 lbs). They sent it for pathology, but the doctor is pretty sure that it was a cyst - nice, self-contained, no signs of malignancy or spread, just really fucking big. And now, I'm going to take a couple of well-earned percs and go to bed. Thanks again, guys <3