This happened to me earlier this year
It was back got a more detailed mammogram, ultrasound and biopsy
The issue got me was a cluster of micro calcifications. Larger calcifications and micro ones which are spread out randomly, are normal. It’s the clustering which they needed to check - can be normal, can be a very early sign of precancerous changed
Now perhaps that’s not relevant to you at all - my centre gave a contact number for a breast cancer nurse who was happy to tell me what was going on (I asked because I worry less when I know what I’m up against - that might not be the right approach for you)
You might have to be in the mammogram machine to guide the biopsy (unless they can see what they need to get at by ultrasound). You should get plenty of local anaesthetic.
It took about a week to get results. Mine were inconclusive so I needed a second biopsy. Second results more of less clear - no cancerous or pre-cancerous cells, but some aplasia of unknown significance, so I’m on annual recall for 5 years
Some people who have been recalled, they said. don’t even require a biopsy as the detailed mammogram shows no cause for concern. Lots of people get an all clear after first biopsy.
I’d say you don’t need to be at panic stations, but go be kind to yourself, because even though it is hugely more likely to be something inocuous it can still be a pretty stressful time.