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Not necessarily, they probably did a bunch of blood tests and scans and picked it up then.Kinda mad it was in a way fluke they caught when performing another surgery.
If they do any imaging at all for example they'll be looking for the issue that they've booked it for, but also look for anything else out of the ordinary in the x-ray/scan and a lot of the time they'll get a lot more in the imaging that just the area they're interested in.
My father had a scan as a precaution for one thing, and found a lump in a completely different place which as the consultant put it "caught it really early" because normally they only start looking for it once there are symptoms.
One of the reasons to always get any precautionary scans/tests the doctor offers, the issue they're actively investigating might be minor, but you never know until they've done it, and you never know what else they'll find.