I have only attended a clinic after a mammogram came up with something.
They go all out to be able to give you an answer on the day, so you have mammograms (more thorough and more focussed than the screening ones), examination and ultrasound.
If they are not sure, then they will do a biopsy on the day and you will have to wait for those results. If it is a cyst or something like that, it can be dealt with on the day.
Everyone was very nice, helpful and from my experience, very thorough (they did not find anything, but tried very hard

)