Hi @Elli,
I am sorry you find yourself here. It is all such a shock at the start and very overwhelming. There is so much to learn about, like a whole new language.
Many breast cancers are hormone positive which means that the cancer may be sensitive to those female hormones of oestrogen and progesterone. That means that the cancer grows with those hormones.
When this is the case many women are put on hormone suppression treatment as part of their breast cancer treatment. This usually happens after surgery, chemo and radium if any of these are part of the treatment.
I think Mirena's are based on progesterone which probably why your oncologist wants you to remove it before chemo or other treatment. Your oncologist would want your treatment to be effective and not less effective because of the mirena.
If you are unsure of the reasons you should talk to your oncologist again so you can get clarification. If you see the oncologist tomorrow for your results it is good to take someone with you. Also write down all the questions you have and get the answers so you are confident going forward with your treatment.
I can't tell you the impact of removal of your mirena but try not to get too far ahead of yourself. This breast cancer journey is alot to deal with and it's one step at a time. Deep breaths help too.
Try to keep busy till you start treatment, drink plenty of water, try a little exercise if you can too. It all helps. Everyone here is very helpful and you can ask anything. Someone always seems to answer.
Let us know how you get on with your results if you want too. I hope your appointment tomorrow goes well. Best wishes 💐