Diagnosis can take a while and the wait is aweful. When you go back they will have all the results they need to give you a fairly definitive treatment plan. They will also be able to give you a provisional date for surgery so you can start planning. 
The biopsy will give them a provisional diagnosis, the type of cancer, whether it is hormone and/or herc positive. The size of the lesion and what grade it is. They will be unable to stage it until you have the tumour removed. 
The biopsy may indicate a benign tumour, although radiologists are pretty good at spotting cancer using mammogram and US. 
Having just gone through the process I decided to prepare for the worst, anything else would be a bonus. This meant I was able to take in most of the information I was given and ask questions. 
I was diagnosed with a 28mm grade 2 ductal carcinoma which was ER+. It is treatable. They won't stage it until all the biopsies are back next week. I am a week on from surgery but it is no longer inside me, part of it is in California being oncotested the rest along with 4sentinal lymph nodes is 12 miles away in the path lab. There may be cells left but I will be having radiotherapy in a few weeks to blast them. Maybe chemo ahead of that if oncotest shows a high percentage of genes present in the tumour.

I know a lot of women who have had breast cancer, some with secondary cancer . The majority have survived and even those that have been given a terminal diagnosis have carried on living for far longer than they hoped. My sister is one of them, she will celebrate 20 yrs survival next year and has remained cancer free. Her cancer was more aggressive and triple negative so it gives me hope. I have also got to keep my boob, my sister didn't and chemo robbed her of the ability to have a family. 
I am a glass half full person so whatever the future brings what will be will be.

Hood luck with your next appointment, relax for now you cannot change things but you can carry on with life until then. 

Thank you so much for replying Angrymum and for your words of wisdom. I'm sorry you're going through this too, but glad it's treatable for you. I just want to get on with doing whatever needs done - it's hell waiting for the results, even though I pretty much know what they will be. I'm trying to remain positive and focus on good news stories. I have 2 kids and want to be there for them for as long as I possibly can! I hope you have a speedy recovery from your surgery and hope all goes well for you.

Breast cancer is very survivable my friend is 24 yrs post mastectomy, she's fine. 
Take any questions you have  with you written down so you don't forget about them. 
The clinic are very good and able to help you come to terms with everything.  
 

Susie

Thank you so much Susie [@Alfieisastar]‍ I really appreciate you taking the time to comment. This is the sort of thing I need to hear right now. The thought of possibly leaving my kids behind is the worst thing about this whole situation. Xx

Morning JJ, I thought I'd replied to this, but I seem to have lost it.  I'm going to post the below on another feed, but wondered if it might help you - you're not alone. Mickey

So I’ve my initial diagnosis after speaking to the breast care nurse yesterday because it was all getting just too much.  She was lovely and is going to see me after my stereotactic biopsy on Tuesday morning (12/10). My lump is mucinous cancer (which I’d never heard of), but apparently is the least aggressive. But I also have a cluster of microcalcifications in a different area of my breast that are DCIS. Also there is a clear width of pre cancer behind it and sides of lump. I will need surgery, but they need the result of my stereotactic biopsy before they can look at my full treatment plan. I am oestrogen receptive positive (score 8/8), which I’m told is very positive. I don’t know if that’s different from HER+? I just know I’ll need anti oestrogen tablets and obviously need to stay off HRT. 

I’m glad I know, I knew it was cancer, but I wasn’t expecting to have a ‘greedy boob’ with more than one.  

Thanks for reading this. Mickey xx

Morning JJ, I thought I'd replied to this, but I seem to have lost it.  I'm going to post the below on another feed, but wondered if it might help you - you're not alone. Mickey x  so I’ve my initial diagnosis after speaking to the breast care nurse yesterday because it was all getting just too much.  She was lovely and is going to see me after my stereotactic biopsy on Tuesday morning (12/10). My lump is mucinous cancer (which I’d never heard of), but apparently is the least aggressive. But I also have a cluster of microcalcifications in a different area of my breast that are DCIS. Also there is a clear width of pre cancer behind it and sides of lump. I will need surgery, but they need the result of my stereotactic biopsy before they can look at my full treatment plan. I am oestrogen receptive positive (score 8/8), which I’m told is very positive. I don’t know if that’s different from HER+? I just know I’ll need anti oestrogen tablets and obviously need to stay off HRT. 

I’m glad I know, I knew it was cancer, but I wasn’t expecting to have a ‘greedy boob’ with more than one.  

Thanks for reading this. Mickey x

Hi Mickey, thank you for sharing. I'm still a bit overwhelmed at all the different types and terminology - I had no idea! But I'm glad your cancer is non-aggressive and I really hope all goes well with your next biopsy and you can make a full recovery after surgery. It's scary isn't it, but good to hear from others going through it. Wishing you strength and luck xx

Hi JJ, yes, it's very overwhelming and confusing. Thank you and I'm sending you that virtual hug. We will get through this  scarey time and come out the other side x thinking of you too and let's keep each other posted so those virtual hugs remain in place xx love n hugs Mickey x 

And hugs back at you! We will totally get through this! Yes, please keep in touch. My next appointment isn't until 19 October so just praying the time doesn't drag too much. Jenny x

Hi Jenny, I won't get my results of Tuesdays biopsy for a few weeks and so we'll support each other through xx trying to keep busy is hard I know, I can't switch off from it - but we've got to try xx more love and virtual hugs Mickey x