On pins and needles

I am 33, have a 7 and 5yr old. Breastfed both of my babies. At the end of July I found a lump in my right breast. Went in to see my primary care physician and was referred to the "Breast Clinic". My PCP stated that she was not concerned. Went to "specialist". Specialist also stated that lump was likely a cyst and that it was not at all suspicious. Was referred for mammogran and ultrasound (for cyst confirmation) At Mammo/u/s Radiologist stated that it was a cyst and that I had nothing to be concerned about. He asked that I continue self breast exams and my annual physicals w/ my PCP. At my follow-up with specialist (following Mammo & u/s) he reviewed my results with me and confirmed lump was a cyst. He then proceeded to aspirate the fluid from the cyst (to avoid any discomfort it may later cause) and said he would send it in for testing (apparently most dispose of this fluid be he routinely sends in). Last Friday he called and told me that the lab results were back and that they had found a small amount of atypical ductal cells and histiocytes in the fluid sample. While it was in small amounts he requested a biopsy (scheduled for next week). I am completely dumbfounded. How were my Mammo & u/s exams completely normal yet the sample abnormal? I seriously feel sick to my stomach. I do not know anyone (personally) in my age group that had ever dealt with this. Everyone I know who has had a cyst and has gone in for Mammo & u/s and had normal results has never had the fluid aspirated and tested. I am scared out of my mind. My mind keeps going to very dark places. Has anyone been through my scenario? Please help with any feedback.