Update: Things look good, although they do want to see me again in 6 months.
I also saw someone I knew in the waiting room; she was there for the same thing, and was a former volunteer at the library. I invited her to come back, if she wishes to do so, and seeing her really cheered me up.
It looked like they were doing all re-checks this afternoon, because that’s when the doctor was there to do real-time readings.
Update: I had the scheduled mammogram again today, and things are looking stable. It’s a small calcified area near the location in my left breast where the cancer was, and it hasn’t changed, so they said “see you in 6 months!”.