Hi there
I was in a slightly different situation to you - my tumour was also lobular , was not picked up on mammogram -,I found a lump
Due to the size - 5.5cm - my surgeon recommended a mastectomy straight up which I had.
I ended up getting the other one removed and double DIEP reconstruction after having radiotherapy ( again recommended due to size of tumour)
These are extremely difficult and personal decisions to make that is for sure.
I was large breasted (E cup) but took the opportunity to go down to a C cup and 28 months on from the reconstructive surgery zi am very content with my decision.
At my first consult my surgeon talked about the possibility of a lumpectomy but the MRI clarified the extent of the tumour and my surgeon said after the mastectomy we made the right call.
Best of luck with whatever you decide .