Understanding Discrepancies in Breast Biopsy Results: Fine Needle Aspiration vs. Surgical Biopsy

Question
I had a fine needle aspiration done and I guess some Atypical cells were found, so they sent me to have this small breast nodule removed, and from what I was told, there was no Atypical cells in what was removed.  HOw can this be?  Is this common?  The Surgeon mentioned something about the Needle aspiration could have caused some  inflammation, and that could have done it.  I guess I just don't understand.    How could the needle catch some Atypical cells but not the Excisional biopsy?   Thanks  

Answer
Well Renee, I suppose you have had some Pap (Papanikolaou) cytologigal tests done too by your gynecologist, right? As you surely know that is a cytological test taken from the cervix of your uterus in order to find any signs of cervical cancer and to do it early. Now there is a "grey zone" between normal cells and atypical cells indicating an early development towards malignancy (early pre-cancer development). That is a very common situation when you do Pap cytological smear tests, so often you have to do one or several follow up test(s) or a surgical biopsy (where often nothing is found, the reason for the cytological finds often being a gynecological infection/inflammation NOT a tumour). Often you have no apparent reason for your finds too - at least not at present. You have a similar situation with thin needle aspiration cytological biopsies
where, as in your case, in unclear situations you have to make a surgical biopsy. That is then the important test to find if there really is a tumour or not. In most cases though it is enough with the needle to show that there is no cancer. Unfortunately you were one of the exceptions. But look at it this way. By doing both tests you can now be SURE that there was no dangerous tumour! Good luck!