Here I go again.

I am 25 months post mastectomy, 4 rounds of TC chemo, no radiation, was then put on Exemestane which apparently is the rolls Royce of Tamoxifen and a Zoladex injection every 28 days. First diagnosed in July 2015, I decided on mastectomy. Tumour was measuring 4.4cms and was found to be very aggressive. Most common form of b/c was diagnosed, being 90% oestrogen and 90% progesterone positive. At my 2 year annual checkup a mass measuring 1.8 x 1.0 cms was detected in my other breast, this was not there 12 months ago. Biopsy has been performed and sadly this is another visit from breast cancer for me. My original surgery showed there to be NO lymph node involvement and the only reason for me having 4 rounds of chemo, as a precaution, was due to the aggressive nature of the tumour. My multidisciplinary team has told me that this is nothing to do with the original cancer and that this is extremely random as it only happens to 6% of women who have previously dealt with b/c. 
This cancer is a 2nd primary and not a secondary from the original. There are no reasons as to why this has happened and I am struggling to get my head around it. I now have to make the decision as to whether I have another mastectomy or opt for the lumpectomy followed by radiation. Any advice, suggestions or information from others who have found themselves in this same situation would be greatly appreciated. Love to all xx