We just got off the phone with Dr. Pandya. The biopsy did not hit the tumor as well as they would have liked, so all the conclusions are iffy. But it's definitely not a recurrence of breast cancer, which was the worst possibility. It's also probably not a recurrence of the GIST, which is what we were expecting.
The best explanation so far is a third kind of cancer, one that is extremely rare: epithelioid angiomyolipoma. (I had never heard of it either.) It's sufficiently strange that there aren't statistics worth mentioning. You take it out, and most of the time it doesn't come back, but sometimes it does.
All in all, that's a better deal than either of us were expecting: liver surgery, which looks tricky but is probably doable, and then we wait and see, with some reasonable amount of hope.
And remember: That's all still tentative. There were some other tests they want to run, the GIST recurrence is not completely ruled out, and Pandya hasn't got a definite I-can-do-that from the liver surgeon yet.
She's planning to call us back tomorrow.